When your health drops to zero, you’ll be incapacitated (immobilized on the ground) until a teammate revives you. While incapped, you will have a “bleed out” health bar that will slowly count down. If no teammates come to revive you, you will die.

When you see this, run up and hold to revive them. Repeat until you reach 50 revives. This will take less time than you think. Playing on Expert with computer controlled survivors will net you quite a few revives.

This can be done very easily. At the start of No Mercy, just have a teammate fall off the buildings ledge and then just pull them back up. Rinse & repeat. It counts as a revive and you will unlock the achievement a lot faster than friendly firing your teammates.

First aid kits can be picked up either at the beginning of levels or in safe rooms. You can only carry one at a time. When a fellow survivor is hurt, press to equip the first aid kit then get next to the hurt survivor and hold to heal them.

It’s cumulative, so it doesn’t have to be done in one campaign.

Pain pills can be found lying around if you look hard enough. If you are near some, a pop-up on your screen should point you to their exact location.

When a fellow survivor is hurt, press to equip the pain pills, then, press to give it to them. Playing through any campaign will easily get you this achievement.

When a survivor is being attacked by the Infected, this is your chance to protect them. This can also be achieved if a survivor is incapacitated and lying on the ground being attacked.

So if another survivor is getting attacked and you shoot the Infected, this is counted as protecting. It will come eventually as you play through the campaign. It should say “Francis protected Zoey”, (or something like that) on the left of your screen.

If you see a Hunter, right when he is about to pounce, just press to melee him. If you don’t succeed the first time, there are plenty of Hunters to try again. Start up the No Mercy campaign on easy difficulty on the Apartments, and once you get outside, there should be more than a few.

You’ll know if there’s a Witch nearby if you start hearing creepy crying. A witch will be lying on the ground, weeping into her hands. You must get her attention first. Just walk up and turn on your flashlight and she will look at you before standing up. The second she looks at you, shoot her head with the semi-auto shotgun.

At the end of a campaign, you need to call for a rescue vehicle in order to get out alive. Once you do so, a hoard of Infected will attack. Try and fend them off as much as possible, without anyone getting injured. An easy way would be to use a pipe bomb which will cause the Infected to be attracted to it, thus making it easier it for you get away.

Follow this video's instructions and you should be fine:

See "No Smoking Section."

Start a No Mercy campaign on easy and begin in the Apartments. Find a pipe-bomb and equip it by pressing . Continue through the level until you find a Boomer, and when you do, get close enough for him to vomit on you. Once he dies, throw the pipe-bomb by pressing . The pipe-bomb should distract the Infected away from you, with just enough time for you to gain back your vision.

This is not as hard as it seems. This can be done with 3 other people who can shoot any weapon they want, just as long as you only fire pistols. You cannot use the minigun.

Start the No Mercy campaign on easy, and when you start, just don’t pick up a weapon. Punching, pipe-bombs, and molotovs don’t cancel out the achievement, so go ahead. This must be done in one sitting. You can't quit out and then continue from where you left off.

During a campaign, if one of the survivors dies, they can come back if you rescue them from a closet. You should see a pop-up on your screen to rescue someone nearby. They appear as an orange outline on your screen.

The Subway mission in No Mercy has plenty of closets if one of your survivors dies. Once you see a survivor in a closet, open the door by pressing .

When a Hunter pounces on a survivor, you will be alerted to save your fallen comrade. Just run up to the attacking Hunter and press to melee him off the survivor. In the No Mercy campaign, there should be more than a few Hunters.

Start a No Mercy campaign on easy and begin in the Apartments. Once you get outside, there should be at least one Smoker waiting for the Survivors. The second you are grabbed by a Smoker is the only time you can free yourself by shooting him. Smokers have a green mist that follows them around, so they can easily be spotted. Just watch him until he shoots his tongue at you, then shoot him immediately.

Start a No Mercy campaign on easy and begin in the Apartments. Once you get outside, there should be at least one Smoker waiting for the Survivors. Let one of the other Survivors get attacked and dragged by the Smoker’s tongue. Once this happens, instantly start shooting the Smoker until he drops the Survivor. If you play through the campaign, it should come pretty fast.

To set Infected on fire, you must throw a Molotov cocktail or pipe-bomb at them. Molotov cocktails are recommended because they have a huge blast radius so this makes the achievement pretty easy. Also, look for gas cans that you can pick up and throw. Shoot the gas can to produce a large fire.

If you see a horde of Infected heading towards you, press to equip the molotov or pipe-bomb, and once you see a large amount of Infected, toss it into the middle of them by pressing . They will run right through the fire at you, setting themselves on fire in the process. If you threw a pipe-bomb, the explosion should set 10+ Infected on fire.

You can find Molotov cocktails and pipe-bombs lying around on shelves and floors during the campaign. It’s cumulative, so this doesn’t all have to be done in one campaign.

Doing this with 3 other people is the best because the computer controlled characters have a bad habit of shooting at the witch. Start on the No Mercy campaign on easy, and if you start hearing crying, it’s a witch nearby. Turn off your flashlights by pressing , and don’t fire a weapon or throw pipe bombs. You should see her lying on the ground, weeping in her arms. You must pass behind her, because she will see you if you walk right in front of her. Also, try not to look at her, as she will notice you staring… Once you get past the witch, you're home free.

I recommend doing this with 3 other players because the computer controlled players will shoot the Tank, thus ruining your achievement chances. Or you can just start on No Mercy in the Subways on normal. When the game starts, kill the AI players and just go through the chapter until you run into a Tank.

They appear very randomly and you will feel them coming. When you do run into a Tank, tell your fellow survivors to let you take him one on one, it should take a few shotgun shots, but if you are playing on normal, it won’t take long. Throwing a molotov on him will make his health go down very quickly also.

I recommend doing this with 3 other players so you don’t have to worry about the computer controlled characters getting hurt.

They appear very randomly and you will feel them coming. When you do run into a Tank, just stay as far back as possible, but continue to shoot him. He should go down pretty quickly on easy if you have all players shooting.

This can easily be done on easy in single-player. Because the 3 other survivors are computer controlled, they will rarely shoot another survivor by accident. You still need to be careful around them though. Just as long as you can control your own fire, you should be able to get this achievement with no trouble. This must be done in one sitting. You can't quit out and then continue from where you left off.

Begin the No Mercy campaign on easy. Everyone must survive the last horde of Infected and make it into the rescue vehicle to get this achievement. It doesn’t matter if you have almost no health left, just as long as everyone walks into the rescue vehicle alive. This must be done in one sitting. You can't quit out and then continue from where you left off.

Start a No Mercy campaign on easy with 3 other players. If you play with computer controlled characters, they might run up and heal you without you knowing. If you do start getting healed by them, just equip a medpack or pain pills by pressing or and they will stop.

You must make it through the entire campaign without healing yourself or be healed with a med kit. You can use pain pills. Try and stay back while the other survivors kill all the Infected. Don’t worry if you become incapacitated or killed, it won’t count as being healed.

See "Cr0wned." While going for that achievement, you will get this achievement, too.

Mounted machine guns are usually at the very end of missions to protect you from the final horde of Infected. It’s cumulative, so you don’t have to get this in one campaign.

Campaigns and chapters with mounted machine guns:

No Mercy

• Half-way point of the Subways
• End of the Finale

Death Toll

• Half-way point of the 4th chapter
• End of the Finale

Dead Air

• End of the Finale

You can check your status on this in the Achievements Screen.

This is easily achieved by starting up the No Mercy campaign and beginning in the Subway. If you look around, you should be able to find a pipe-bomb. Press to equip the pipe-bomb, and once you see a large amount of Infected, toss it into the middle of them by pressing . The beeping from the pipe-bomb attracts the Infected, so it should draw a lot more after you throw it.

Playing through the entire game on Easy should net you quite a few kills. Good thing the game has tons of re-playability because it should take you quite a few play-throughs to achieve this goal. It’s cumulative, so you don’t have to get this all in one sitting.

During each 'movie', I got about 1k kills with 3 other players on Normal. Playing on Easy would ensure you would get more. If you die and start the chapter over, all the kills you got prior to dying will still count towards the achievement.

There's a little trick for helping you faster, though. See the video below.

A quick way to get this is to start up a split-screen game with another controller.

Start the No Mercy campaign on Expert and begin in the Apartments.

When you start, pick up a first aid kit. Shoot yourself using the second controller, so that your health is really low. Once that is done, shoot someone enough so that you can heal them yourself. Press to equip the first aid kit, and hold to heal them.

You must be under 10, and not exactly at 10.

When your health drops to zero, you’ll be incapacitated (immobilized on the ground) until a teammate revives you. While incapped, you will have a “bleed out” health bar that will slowly count down. If no teammates come to revive you, you will die.

Start up the No Mercy campaign on easy and try your best to kill off all the Infected. You can heal yourself as much as you want, so don’t worry. This is easy if you play with computer controlled players because they will heal you with their first aid kit, too. Be careful, pain pills only serve as a temporary health relief. This must be done in one sitting. You can't quit out and then continue from where you left off.

See "What Are You Trying to Prove?"

You must make it on the last rescue vehicle for it to count.

Get a good team of survivors up with 3 other players and try to go through each campaign. Don’t worry if you die, just as long as one person gets into the last safe room of each chapter, you're good to go. Staying together is the best advice I can give.

This does not have to be done in one sitting. Although, each individual campaign must be done in one sitting.

Start the No Mercy campaign on easy and choose the Subway.

You can find Molotov cocktails lying around on shelves and floors, so be sure to look around. You’ll know if there’s a Witch nearby if you start hearing creepy crying. A Witch will be lying on the ground, weeping into her hands, which should be a good time throw the Molotov.

Press to equip the Molotov, then throw it at her by pressing . Once she is lit on fire, the achievement will unlock. Be prepared to be attacked by her afterword because she’s rather mean, especially because you just torched her.

Start the No Mercy campaign on easy and choose the Subway. You can find Molotov cocktails lying around on shelves and floors, so be sure to look around. You’ll know if a Tank is nearby from the ground shaking. Wait for him to stand still for a second, then press to equip the Molotov, then throw it at him by pressing . Once he is lit on fire, the achievement will unlock.

The Infected can be killed easily from behind by punching them. Just as long as they don’t know you’re there, of course. Start up the No Mercy campaign from the Apartments. It’s easier here because the first Infected you run into, don’t attack right away. Just run up behind one, and press to melee them right in the back of the head.

Start the No Mercy campaign on easy. It's recommended that you do this with 3 other players so you don’t have to worry about the computer controlled characters getting vomited on. You must be careful when turning corners, there might be a Boomer waiting for you. They only take one shot from a shotgun to kill, so use it wisely. If a Boomer explodes on you, it will count as being vomited on. Remember to listen for the Boomer, it makes a distinct sound that you should notice right away.

At the beginning of a campaign, grab the Uzi. It will make it a lot easier to gain headshots over the shotgun. As you progress through each campaign, this will unlock a lot faster than you think. It’s cumulative, so you don’t have to get them all in one sitting.

If you see a Hunter, right when he is about to pounce, just shoot his head clean off with either the Uzi or M16 Assault Rifle. If you don’t succeed the first time, there are plenty of Hunters to try again. He doesn't have to be killed from the headshot, just as long as one bullet hits him in mid-pounce, it will count.

Start up the No Mercy campaign on the Apartments on easy, and once you get outside, there should be more than a few.

Just complete the campaign. This can be done on any difficulty.

This must be done in one sitting. You can't quit out and then continue from where you left off.

At the beginning/end of each chapter, there are safe houses. They are filled with ammo and first aid kits. This must be done at the end of a chapter.

Start up the No Mercy campaign on Advanced and start in the Apartments. When you reach the safe house at the end, enter and then leave it. Then, just wait until someone becomes incapacitated, once this happens, kill the remaining Infected, save them by holding . Then, both of you need to return to the safe room and close the door behind you.

Just complete the campaign. This can be done on any difficulty.

This must be done in one sitting. You can't quit out and then continue from where you left off.

Just complete the campaign. This can be done on any difficulty.

This must be done in one sitting. You can't quit out and then continue from where you left off.

Just complete the campaign. This can be done on any difficulty.

This must be done in one sitting. You can't quit out and then continue from where you left off.

When your health drops to zero, you’ll be incapacitated (immobilized on the ground) until a teammate revives you. While incapped, you will have a “bleed out” health bar that will slowly count down. If no teammates come to revive you, you will die.

The easiest Special Infected to save a survivor from while incapacitated is the Smoker. Once you are incapacitated, look around to see if any fellow survivors are being attacked by a Smoker, or any other Special Infected. Just continue shooting your pistol(s), until you know he’s dead. There’s plenty of Special Infected during the campaigns, so if you don’t do it the first time, just keep trying.

Start a No Mercy campaign on easy and begin in the Apartments. When you see a Boomer, run up to him and press to shove him, then shoot him once with a shotgun to kill him. Just make sure none of the other survivors are nearby to get splashed on.

In Versus Mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. Once the Director chooses you as the Smoker, spawn as far away from the Survivors at that time. This will give you plenty of time to find the perfect spot to drag someone over 100 feet.

When you have found a good position and see the survivors are a good distance away, line up a shot and press to perform your Tongue Snare attack. Once you have caught someone, just try and stay out of the line of fire enough for your tongue to come back with a little treat at the end. This must be done on the same level as the survivors, because you can't drag the survivors up buildings. When you drop the Survivor, the achievement will unlock.

In versus mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. Once the Director chooses you as the Smoker, spawn as far away from the Survivors at that time. This will give you plenty of time to find a spot to constrict the two survivors. After you have grabbed a survivor, the survivor has to make it all the way back to you for you to completely constrict them, thus killing them.

When you have found a good position to attack, line up a shot and press to perform your Tongue Snare attack. Once you have caught someone, just try and stay out of the line of fire enough for your tongue to come back with a little treat at the end.

In Versus Mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. Once the Director chooses you as the Boomer, spawn as far away from the Survivors at that time. Doing this, you can find a perfect spot to hide and wait for the passing Survivors.

Try and hide right around a corner so that all 4 survivors are covered with your vomit once they turn the corner. Press to perform your Vomit Attack. This has to be in one shot so make it worth it.

In Versus Mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. Once the Director chooses you as the Hunter, spawn as far away from the Survivors at that time. This will give you plenty of time to find a good spot to pounce.

In order for you to pounce, you need to be in your primary attack position by pressing . Once you do this, you can press to pounce on an unsuspecting survivor. Now press over and over again to claw your survivor to death. Once the survivor is dead, or you are punched off, you can pounce again.

In Versus Mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. Once the Director chooses you as the Tank, find the survivors as fast as possible. You have to attack them before your 'Frustration Meter' runs out. If it does, you will lose control of the Tank.

The Tank is a very strong and powerful Infected. You can take very many shots which should make it easy for you to kill the Survivors. If you want to keep your distance, press to pick up objects and throw them. This can deal a lot of damage so I recommend it. If you are near the Survivors, just press to punch them.

You only have to incapacitate all 4 survivors, you don't have to completely kill each survivor. Knocking a car into the Survivors will incapacitate them usually in one hit.

In versus mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. The Boomer doles out the most damage in the quickest time because every hoard you attract, counts as damage from you. This is cumulative, so it doesn’t have to be in one match.

You can check your status on this in the Achievements Screen.

In Versus Mode, you must be on the Special Infected team. The Director will randomly choose what Special Infected you spawn as, but you will be able to choose where to spawn. A survivor must enter a safe room, then leave it after for this to count. Once you spawn as the Special Infected, try and get to the very end of the level. This could only work if they entered and exited the safe room at the end of the chapter.

Start the campaign on easy with bots or online with friends and breeze through it. You can get this online or offline.

The idea behind the achievement is not to take a break and restock on ammo and such. Set up a game on easy and just stand next to the power generator at the last stand and let the bots do most of the work. The lights will go off and there will be an indication on to when you need to re-power it. You can get this online or offline.

Play the campaign online, offline or in Versus on the Crash Course until you kill enough Infected to unlock it.

You can do it by yourself via split-screen with bots and another controller or actually do it in public Versus match. You can get this online or offline.

Easily done by yourself with another controller. Make sure you're on the Infected team and let the survivor, which has the other controller and bots do most of the work until they need to enter the vehicle and just kill them without any getting in it. This has to be done in Versus. Whether it is public with random players, by yourself or with friends, it doesn't matter. You can get this online or offline.

Becoming a Tank is a bit random. Some say the worst guy on the team that is also far away from other infected will become one. Anyway, when you become a Tank, make sure to hit the cars or trash boxes with the right trigger to have it fly at the survivors. You can do it on-line in versus or with set-up friendly match with your buddies or you can do it yourself off-line. In friendly match you can have the other survivors keep reviving the downed ones to maximize the amount toward this achievement.

YouTube - 20 Car Pile-Up achievement guide

The Hunter does pouncing damage. It varies depending on the distance and the elevation of the Hunter relative to its victim. Find a building or other high point and wait for a survivor to come within your distance and just pounce on them. You have to inflect 25 damage points from the pounce alone. You can boost it by playing by yourself offline, with friends online, or in actual public Versus.

YouTube - Jumpin' Jack Smash Achievement

You have to do this in a Versus match where either it has your friends to boost, or a public Versus. You can only do this online. Essentially you need to pull a survivor to you that has been vomited on or exploded on by a Boomer. Meaning the smoker needs to be on the same level as the survivor and pull him. Just drop down right next to someone who has been vomited on and pull them into you.

You can get this online or offline. Start a game in split-screen or join a campaign match. Find a propane tank and when a Tank rushes you drop it in front of him and shoot it. If you are good you can get the achievement via pipe-bomb.

YouTube - Left 4 Dead - Crash Course DLC: Tank

Set this up the same as for "Truck Stop".    The players have to be incapacitated within five seconds of each other. You can boost it with friends, by yourself with a controller or in a public match. You can get this online or offline.

YouTube - Left 4 Dead: Crash Course - Easy

Here's another method:

Use the two controller method with your main account as the infected. Find a safe place from zombies with the survivors. With your guest account shoot each survivor until there is just a little bit of health left on their life bars. When all have just a tad bit of health, start the team killing. Shoot each one a few times quickly to down them all and the achievement should then unlock for your main account.

Simply complete The Sacrifice campaign in one sitting. This can be done on any difficulty. The chapters in this campaign are:

• The Docks
• The Barge
• Port Finale

One of the new things in this campaign is the finale requiring one of the players to "sacrifice" themselves in order to complete it. First, you have to activate three generators scattered around the map. To do so, approach one and hold . After the bridge is lowered, you will have to press a button on the platform. Doing this will cause a generator to shut off. One player will have to leave the bridge and re-activate the generator while the others must stay on the bridge.

To obtain the achievement, the person playing as Bill must go down and re-activate the generator. This can be done by yourself easily by selecting "Port Finale" as Bill on easy difficulty on single-player. Get up to the finale and proceed to activate the generator. If you are playing in single-player, you must do this, as the bots aren't programmed to do so.

Scattered throughout the levels are white barrels that look like the ones in the achievement. Surely enough, if you shoot one enough, it will explode.

Now, an easier way to do this achievement than blind luck is to get 1-3 more players with you. Kill off any AI Survivors before doing this. Start the campaign on any level until you find a barrel or two. Next, position a player near the barrels until a Hunter comes along (turn on subtitles to know when one is around). Step away from the player near the barrels and the Hunter should pounce on them. Shoot the Hunter a few times with an automatic weapon, then blow up the barrels. The Hunter will die, and you should obtain the achievement.

Now, at first glance, it seems you just need to turn on all three generators. Unfortunately, that is not the case, as you need to activate them all at the same time. You will need 1-3 other people (depending on whether someone can use a controller). Start up "Port Finale" on easy difficulty and position each player or controller next to a generator. Next, have everyone hold at the same time until all three generators are activated. The achievement should pop up for everyone afterward.

This achievement can be pulled off with 5 people if done correctly. Have 1 person be a Survivor, while the other 4 (including you) are the Infected. Make sure the Infected team do not spawn until the bridge is raised. When the generator is turned off, have the one player leave the bridge to turn it back on. This is when you and the other Infected team spawn. Have the other 3 Special Infected keep the AI Survivors distracted as you attempt to incap the human controlled survivor. It is recommended that a Hunter or Tank incap the survivor. Once the human survivor is incapped, you will earn the achievement.

NOTE: The player does not have to be turning on the generator. They only need to be off the bridge.