Stringing combos, dodging at the right moments, and making good use of your kicks and breakers are essential to earning this one.

Perform basic and special moves to fill your kick meter. Once done, simply lift your knee to perform a close-combat move.

When your opponent is rushing in towards you to do an attack, lift your knee to kick them and you will counter their attack.

To dodge, lean your body to the left or right, just as your opponent initiates their super move. This will be taught to you during training challenges.

With any character, initiate their first super move, then immediately follow up with their second super move. 

See "Maximum Combo" for more details.

With your first character, execute their first super move, followed by quickly tagging in your partner and finishing it off with their super move. This will be taught to you during training challenges. 

See "Maximum Combo" for more details.

Similar to the Tag Combo achievement, except you must switch characters twice. To do this, start with their first super move, next, tag in your partner and do their first super move, then tag your first character back in and finish it up with their second super move. 

See "Maximum Combo" for more details.

During fights, you'll notice there are four poses at the bottom of the screen. The first one will show you how to tag your partner in, while the other three represent how to do your character's super moves. As far as super moves go, the first two will always knock your opponent into the air; they are known as launchers. Depending on the character, their third move will vary between a launcher and a projectile move. Most projectile based moves usually end the combo. See the picture below for more details.

In order to do combos, you must chain super moves together quickly. You can chain bigger combos if you initiate their moves in order from left to right, and by swapping your partners in for additional tag combos.

For this particular achievement; start with a launcher attack, then immediately tag your second partner in and do their first two super moves. (make sure your second super move ends with a launcher) Finally, tag the other partner back in and follow up with another one of their super moves.

Note: Some of the combo achievements have been reported to be glitched. Just keep trying and it may randomly unlock.

Here's a video to show you how combos should be executed. 
Marvel Avengers: Battle for Earth (Maximum Combo Achievement/Trophy) - YouTube

There are certain super moves that can counter others. For example, Magneto has a move where he launches in the air to charge his Magnetic ball. While he’s in the air, you can use someone like Wolverine, who has a special move that will rush in and uppercut him while he’s still airborne. There's a training challenge that requires you to learn this.

At the bottom right of the corner, you'll notice a meter start to fill up whenever you attack, or get attacked. When the meter is half way filled, the announcer will say "Breaker," letting you know it’s ready. Simply jump to use your breaker, but make sure to initiate it when you're caught in your opponent's combo.

First, you must fill your ultra meter. You can do this by performing basic and super moves; the meter also fills when you're attacked. When the meter is half way filled, you'll be able to do a breaker. Make sure you don't use it or else the meter will drain all the way down. Instead, keep fighting until the meter is 100% filled. When you have it, the announcer will say "Ultra Ready." Now simply lift your knee and you will start the ultra move. The achievement will unlock shortly after.

All you have to do is win a co-op match in either campaign or arcade mode. It should pop up during the results screen. 

Note: This one seems to be a bit glitchy for some; restart your Xbox and try again. Refer to the video under "Symbiosis" to see exactly when mines popped.

The best way to execute this one is to start with a launcher, switch characters and do two of their super moves, (Second move must be a launcher) switch back to your original character and finish with another one of their super moves to make that a 4x combo. Black Widow is a good character to use because all three of her super moves end with a launcher.

Note: This one looks to be a bit glitchy for some. Restart your Xbox and try again.

It may seem a little complicated, so you can check this video out if you need more assistance.
Symbiosis & Power Duo Achievement/Trophies - Marvel Avengers: Battle for Earth - YouTube

Trials are various challenges that will put your skills to the test; some will be easy, others will be a pain. There are 20 challenges for you to complete. The first 12/20 trials are already unlocked, while the last 8 will require you to purchase them for 40 points via UPlay. (UPlay can be accessed from the Main menu.)

Note: You will earn UPlay points for earning these achievements.

• 10 points - Here I Am
• 20 points - King of the Hill
• 30 points - Earth United
• 40 points - Earn "Closure

Tips: Making sure to use dodging effectively and always time them well. String together combos and tag combos for maximum damage. Anytime you're in a jam, use that combo breaker! Often you can start off with a combo breaker in order to kick off a tag combo. Finally, and most importantly, read to the challenge description! That may break up a lot of confusion when you're trying to complete those lessons.

You must complete 5 super moves in a row with "fast timing." When doing super attacks, you will notice a pop up that will say fast, normal, or slow. Depending on the super move they're currently doing, each character has different timing. It doesn't necessarily mean that you have to execute each move very fast; it's more about how well you time their move. See the video under "Adamantium" for more help.

Costumes can either be unlocked via Campaign, challenges, ranking up, or bought from the marketplace. After choosing your character, simply hover over them and slide your hand to change their costume. The achievement should pop immediately afterwards.

Simply win the match without dodging to the side and make sure you stay in the sights of the Kinect sensor.

You gain ranks by earning experience points. XP is earned by doing basic moves, super moves, and using great defense. Try to aim for an A rank or better. When you finish Campaign you should be at least half way there to your goal. The fastest way to earn XP is by playing versus mode and making sure you’re the only one playing. When the match starts, just beat up your opponent using combos and tag combos. You will earn more XP if you create longer combos. After the match, skip every cut scene, hit rematch and repeat until you have the highest rank.

Note: The average amount of XP you should earn is about 3,500 and matches typically take 30 seconds to complete. Based on my previous statement, if you had started from scratch, it would take you about an hour and a half of pure boosting or about 160 total matches.

The Video below shows how to boost this achievement quickly.
Marvel Avengers: Battle for Earth - Boosting method for Legend Achievement - YouTube

When playing campaign, you'll earn this halfway through the story. See the Legend achievement for more info.

This achievement is self-explanatory; see "Part of me" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

This achievement is self-explanatory; see "Part of me?" for more info.

First. you must unlock these characters by playing through campaign. They'll unlock after every other match. Once the characters are unlocked, choose them and win a match in either Arcade, Versus, or tournament mode.

There are two parts to campaign mode, so you will unlock this one after you complete the first half of the game; which will be 20 fights. There's a progress bar on the select screen of campaign mode, so you will know how far you are. See Closure for more info

Note: This also nets you 30 UPlay points.

Campaign mode is not very long at all; it consists of 41 total fights. There are five cities that contains eight battles each, with one of them having a ninth and final battle at the end. 

Tips: Make sure you string special moves back to back for maximum effect. Try to dodge incoming attacks, and use your combo breaker if you're ever caught in your opponent's combo. Once you get the hang of playing, fights typically last 30 to 60 seconds.

Note: This achievement may be glitched, so before your last few fights, I highly recommend that you create an additional save on a separate memory device, like a flash drive. This is so you don’t have to complete the whole campaign over in case this doesn't unlock for you. Also nets you 40 UPlay points

There are 20 characters with 16 lessons each. Every character should take about 10 minutes each to finish.

Character Challenge Tips: Time your moves perfectly; it's not all about how fast you string your moves together, but more relative to how well you time them. Try to aim for a "fast" move selection. (An on-screen text will pop up.) Another thing to keep in mind is if you're too far away to hit your opponent, then you may have to kick in order to move in closer to be able to attack them. In certain sections of challenges, you will be required to avoid attacks; in order to do this, you have to dodge them by leaning to the side. Make sure you dodge their attacks at the EXACT moment they strike you or else it may not count.

Simply complete arcade mode for the first time and the achievement is all yours. There are about 10 matches in total and will become a little harder the more you advance.

A lot of people might get confused by this one, because there is a tutorial mode for you to play towards the main menu; but it's not technically the tutorial challenges they want you to play. To get there, select Fight modes > Challenges > Training. Now complete all 5 of the challenges and the achievement should unlock.

Self-explanatory; when playing one of your earlier matches in campaign, just make sure you win without switching your character. Very easy to do.

Adamantium is the highest possible grade you can earn in a match. The amount of XP needed is 4,000. You earn XP by doing basic moves, super moves, and you also earn xp based on how well you defend yourself. An easy way to earn this is to start a 2 player versus match and play by yourself. When the match starts, just string combo and tag combo super moves together and by the end of the match you should have earned enough for the achievement. 

Here's a video in case you needed help.
Marvel Avengers: Battle for Earth - Adamantium Grade Achievement/Trophy - YouTube

Simply start campaign and win your first match; it's that simple.

For this one, you must build up your Ultra meter by using Kicks, punches, and special moves. It also builds up whenever you take hits as well. Once the meter is completely filled, simply jump to activate and your character will do the "Ultra" animation. When prompted you and your buddy have to punch at the same time during the "beat 'em up" sequence and the achievement should unlock.

Tournament mode consists of three to four teams. Win by eliminating other teams each match to advance to the finals. This mode is split screen multi-player only, so that means you can’t play against bots. Luckily you can start tournament mode by yourself and just destroy your opponents to earn this one with ease.