Disable AI:
Go to the main menu and highlight Arcade Mode. Then press: UP, UP, DOWN, DOWN, A, A, B, B, X, X, Y, Y.

Unlimited Supers:
Press UP, UP, DOWN, DOWN, A, X, A, X.

Unlockable: Bonus Characters:
Bastion: Beat Story mode with Magneto without losing.
Bishop: Beat Arcade mode with Gambit.
Blob: Beat Arcade mode with Bishop.
Dark Phoenix: Beat Arcade mode with Phoenix or Story mode with Magneto.
Psylocke: Beat Arcade mode with Betsy.
Pyro: Beat Arcade mode with Dark Phoenix.
Sentinel A: Beat Arcade mode with Cyclops.
Sentinel B: Get 20 wins in Survival mode.

Unlock Bishop:
To unlock Bishop, beat the Arcade Mode with Gambit.

Unlock Blob:
To unlock Blob, beat the Arcade Mode as Bishop.

Unlock Dark Phoenix:
To unlock Dark Phoenix, beat Arcade mode with Phoenix.

Unlock Everything:
On the Main Menu, press UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, A, B, START, START.

Unlock New Costumes:
Beat Arcade Mode with any mutant to unlock third costumes for everyone.

Unlock Psylocke:
To unlock Psylocke, beat Arcade mode with Betsy.