Select "Settings" at the main menu, then "Cheats". Enter one of the following passwords by selecting the indicated characters to activate the corresponding cheat function.
Ant Man mode
Enter Mystique, Spider Man, Hulk, Spiderman, Magneto as a password. In this mode, your player is tiny.
Apocalypse mode
Enter Wolverine, Wolverine, Dr Doom, Abomination, Wolverine as a password. In this mode, everyone has one hit kills.
Black Suit Spider-Man
Enter Spider-Man, Captain America, Abomination, Mystique, Spider-Man as a password.
Captain America's alternate costume
Enter Captain America, Iron Man, Thor, Wolverine, Captain America as a password.
U.S. Agent
Enter Abomination, Iron Man, Dr. Doom, Abomination, Magneto as a password.