Beat Night Crawler
Knock Night Crawler onto the spikes that appear from the floor. Keep punching him, and the spikes will help kill him quickly, often without hitting you back.
Submitted by: Zach
Cyclops
Choose Cyclops when selecting a character. He has no punch combo, so you can continuously punch one enemy till he is KOd without having to stop, unlike the other X-men who can only punch three or four times. Note: This will not work on most Bosses. mini-Bosses and Sentinels.
Play as Bosses
Complete the single-player mode. When you hook up the Game Boy Advances and select a mode, you can choose from Bosses (but not mini-Bosses).
Submitted by: Zach
Beat all Bosses
In this game, Bosses are easy to defeat. To do so, first, pin them against a wall with a rapid punch attack. When they stand up, move to a different level. They will try to get alongside of you, close to the wall. When they do, give them a punch series again. Repeat until they have been defeated.
Special move
Press [A] + [B] to do a special move. Note: This takes away a little bit of life.
Press [Attack] + [Down/Lef. Note: This results in a different move for each character
Submitted by: Zach