Master Cheat Unlock:
Go to the main menu and HOLD L and press Right, Right, left, Left, Down, Up, B.
Get Dark Phoenix:
Beat Arcade Mode using Phoenix
Get Bishop:
Beat Arcade Mode using Gambit
Get Psylocke:
Beat Arcade Mode using Betsy
Get Bastion:
Finish Story Mode using Magneto without losing any matches. You should fight Bastion. Defeat him to unlock him (keep in mind you only have one chance if lose you will have to do the whole story over)
Get Bishop:
Beat Arcade Mode using Gambit
Get Blob:
Beat Arcade Mode using Bishop
Get Sentinel A:
Beat Arcade Mode using Cyclops
Get Character