Free all 50 pigeons in the game. If you are having trouble finding some either switch to Obelix by pressing and the use Dogmatix's pigeon radar by pressing and holding or see THIS list for the locations.

There are a total of eight upgrades that can all be purchased for a total of 6500 helmets from the stand located in the Olympic Village area right outside of where you enter the Olympic events. The stand is open after your first Olympic events are complete. Simply buy them all and you'll get this achievement.

Collect the three glue pots in the game. See THIS list for the locations.

Collect the three bags of magnesia in the game. See THIS list for the locations.

Collect all twelve shields in the game. You will not be able to collect the last shield until you free all fifty pigeons. See THIS list for the locations.

Refer to “100000 Helmets found”

You will get helmets every time you destroy an object or defeat a Roman outside of the Olympic events. As you fight Romans they will drop 'x3' and 'x10' multipliers. Pick these up to increase the number of helmets you receive. After picking one of these multipliers up, you will only have a limited amount of time before it will go away. If you quickly pick up another to add to your multiplier, you can extend the time that it lasts. In big fights you can increase your multiplier to well over 'x100'.

Playing through the game normally you would likely never get near this many helmets (I got roughly 15,000 when I played the game), so you'll have to grind for them. This is best done in the same place as the “100 combo hits achieved” achievement, except it cannot be done in the King of the Arena event.

These achievements are for total helmets acquired not how many you currently have, so feel free to spend your helmets for things like upgrades and health replenishment.

Refer to “100 combo hits achieved”

Each time you land a hit on a Roman your combo meter will increase by 1, you then have a short amount of time to land another hit before your combo meter goes away. Hitting multiple Romans at the same time will increase your meter for each Roman hit (i.e. hitting 3 Romans with 1 attack will increase your meter by 3). Your best bet to get these achievements are in places where an unlimited (or nearly unlimited) number of Romans are available, and using combo attacks like grab and twirl to hit large groups.

I would suggest doing this at one of the following places:
When the Romans are attacking Lovestorix's chariot and you have to throw Romans at the dart board to open the door.
When you're competing in the King of the Arena event (this is when I got it).
Or at the end of the game when you are fighting 1,000,000 Romans. 

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Refer to “Adventure Mode 100% complete”

Simply play through the game in Adventure Mode to the end to unlock these achievements. You can see what percentage you've reached by pausing and checking the "Statistics" screen.

Note that this achievement my be glitched. If you do not receive this achievement after the final battle with 1,000,000 Romans, then you have run into this glitch. At this time there is no known way to fix this other than playing through the game again.

Refer to “Long Jump Winner (High)”

Refer to “Foot Race Winner (High)”

Refer to “Tug of War Winner (High)”

Refer to “Toadball Winner (High)”

Refer to “King of Arena Winner (High)”

Refer to “Hammer Throwing Winner (High)”

Refer to “Javelin Winner (High)”

Refer to “Romanophone Winner (High)”

Refer to “Chariot Race Winner (High)”

The long jump is done by alternately tapping the and buttons to build up speed. Then when you get to the line, press and hold down . When the jump angle indicator is at a good angle (in the green or close to 45 degrees), release the . When you're in the air you will be prompted to do additional button presses to extend the jump.

This achievement can only be done in Olympic Mode.

The foot race is done by alternately tapping the and buttons to run down the track. Do not start running until the announcer says, "Go" or you'll be charged with a false start. As you're running down the track, you may be prompted to press or to hit your opponent and slow him down. If you don't press these when prompted, your opponent may hit and slow down you. When you get near the finish additional prompts will show up in order for you to dive across the finish line. These are not necessary unless it is a close race.

This achievement can only be done in Olympic Mode.

Tug of war is done by rapidly tapping the , , or buttons; whichever is shown on the screen. As the match goes on the button that you have to tap may change, so keep your eyes on the screen as you pound on the button. The high difficulty version is especially hard and people have suggested using the Rock Band drum kit in order to be able to 'tap' the button faster. I didn't find that necessary, but it is a valid strategy.

This achievement can only be done in Olympic Mode.

Toadball is like a mix of soccer (football for those outside the US and Canada) and volleyball. You have to kick the toadballs over the net and on to your opponent's side. You can either do a long kick with or a short lob with . Use the long kick when you are on the back third of the court and facing straight at the net. Use the lob when you are in the center of the court and facing the net. If the ball is in the front third of the net, simply bring it back and use one of the other kicks.

Occasionally a ball will start flashing, if it does this it is going to explode. If the ball is on your side of the net, quickly kick it over as you will lose points if it explodes on your side.

This achievement can only be done in Olympic Mode.

King of the Arena is essentially a giant battle on top of a raised podium. You and your opponent are not fighting each other but a never ending group of Roman soldiers. The goal is to accumulate more points than your opponent. Each hit you land on a Roman gives you points, special moves give you more points, but be careful not to use your charging attack () near the edge of the podium as you can fall off, which will cause you to lose the match.

Occasionally a target will pop up on the edge of the podium. If you grab a stunned Roman (), spin him () and throw him in there ( again) you get even more points.

Whoever has more points at the end of the timed match wins.

This achievement can only be done in Olympic Mode. 

The Hammer Throw is done by holding down the , spinning the as fast as you can counterclockwise and then releasing the when the on screen indicator is in the green zone. Once you pick up the hammer you only have a set amount of time before you'll automatically throw it, so spin fast and release it.

This achievement can only be done in Olympic Mode.

You start the javelin throw by doing warm up exercises, follow the onscreen prompts as these change depending on the difficulty and mode. Then you run down the track by alternating tapping the and buttons. Before you go over the line at the end of the track, press the and release it when the indicator is in the green zone. Once the javelin is in the air, guide it through as many clouds as you can with the .

This achievement can only be done in Olympic Mode.

The romanophone event is like a cross between king of the arena and the romanophone boxes found in adventure mode. You and your opponent are on a platform with different colored Roman soldiers. You must hit the same color soldier as the note shown for you. If you can finish your 'tune' before your opponent you will win.

Things to remember:
The Red soldier will always be in the middle of the platform. The Blue, Green and Yellow soldiers travel clockwise around the edges of the platform, stopping for brief moments at the corners.
If you hit the wrong color Roman, you'll be sent back a couple of notes, so try to always hit the correct Roman.

This achievement can only be done in Olympic Mode.

The chariot race is rather simple, just make your opponent's chariot take more damage then yours. Use the and to charge at your opponent, depending on which side he is on. Use the to protect yourself and release it at the right moment to flip over your opponent. Avoid the obstacles on the course, but try to push your opponent into them. And when you get the bonus boxes, press the in the direction indicated on the screen.

My best advice is to try to avoid the obstacles and try to push your opponent into them. That seems to be the easiest way to win.

This achievement can only be done in Olympic Mode.