Completion Bonuses:
Completing the game unlocks hard mode and Deadpool is unlocked for play. You can also start a game with your current-level characters. Play as Iron Man:
Collect all 4 homing beacons in each act to unlock pieces of Iron Man's Armor. Then after collecting the beacons in Act 5, save Iron Man.
Play as Professor Xavier:
Complete all Danger Room missions.
Age of Apocalypse Costumes:
Complete acts 1 and 2. The costumes will be unlocked in act 3 at an X-Traction point. Press L2 at the character select screen to access them.
Team Bonuses:
Assemble the following teams to recieve the appropriate bonus:
Age of Apocalypse: Any four heroes with Age of Apocalypse costumes: 100% attack rating bonus
Agile Warriors: Nightcrawler, Sunfire, Toad, Deadpool: 5% experience bonus
Brotherhood of Evil: Juggernaut, Magneto, Scarlet Witch, Toad: +5% experience bonus
Bruiser Brigade: Juggernaut, Colossus, Wolverine, Rogue: +20 energy per knockout
Dark Past: Rogue, Deadpool, Gambnit, Wolverine: 5% of damage added to health
Double Date: Rogue, Gambit, Jean Grey, Cyclops: +20 health per knockout
Energy Corps: Gambit, Bishop, Cyclops, Iron Man: 5% damage bonus
Family Affair: Magneto, Professor X, Scarlet Witch, Juggernaut: +5 health regeneration
Femme Fatale: Storm, Scarlet Witch, Rogue, Jean Grey: 5% of damage added to health
Forces of Nature: Storm, Iceman, Sunfire, Magneto: +10 to all resistances
Heavy Metal: Colossus, Juggernaut, Iron Man, Magneto: +10 to all stats
New Avengers: Iron Man, Scarlet Witch, Wolverine, Bishop: 15% maximum health bonus
New X-Men: Nightclawler, Storm, Colossus, Wolverine, Sunfire, Bishop: 15% maximim health bonus
Old School: Cyclops, Jean Grey, Iceman, Magneto, Toad, Professor X: 15% max energy bonus
Raven Knights: Iceman, Professor X, Iron Man, Deadpool: 60% techbit drop bonus
Special Ops: Bishop, Deadpool, Nightcrawler, Gambit: 5% damage bonus