Successfully complete the game to unlock the hard difficulty setting (enemies at level 50). You can also start a new game with your previous characters at their current experience level.
Play as Deadpool:
Successfully complete the game.
Play as Iron Man:
Find the four homing beacons in Act 1 through 4 and collect the piece of his armor that each set unlocks. Then, save Iron Man after finding the four homing beacons in Act 5.
Play as Professor Xavier:
Successfully complete all Danger Room missions.
Use a team with the indicated characters to get the indicated bonus.
Age of Apocalypse (Any four heroes with Age of Apocalypse skins): +100% attack rating
Agile Warriors (Nightcrawler, Sunfire, Toad, Deadpool): +5% experience points
Brotherhood of Evil (Juggernaut, Magneto, Scarlet Witch, Toad): +5% experience points
Bruiser Brigade (Juggernaut, Colossus, Wolverine, Rogue): 20 energy gained per knockout
Dark Past (Rogue, Deadpool, Gambnit, Wolverine): 5% damage inflicted goes to health
Double Date (Rogue, Gambit, Jean Grey Cyclops): 20 health gained per knockout
Energy Corps (Gambit, Bishop, Cyclops, Iron Man): +5% damage
Family Affair (Magneto, Professor X, Scarlet Witch, Juggernaut): +5 health regeneration
Femme Fatale (Storm, Scarlet Witch, Rogue, Jean Grey): 5% damage inflicted goes 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
New X-Men (Nightclawler, Storm, Colossus, Wolverine, Sunfire, Bishop): +15% maximim health
Old School (Cyclops, Jean Grey, Iceman, Magneto, Toad, Professor X): +15% max energy
Raven Knights (Iceman, Professor X, Iron Man, Deadpool): +60% techbit drops
Special Ops (Bishop, Deadpool, Nightcrawler, Gambit): +5% damage
Complete Act 1 to unlock the Snow Iceman, Brown And Gold Wolverine, Original Cyclops, 70's Cyclops, Original Jean, 70's Jean, 70's Nightcrawler, 70's Colossus, and 70's Storm costumes.
Complete Act 2 to unlock the Age Of Apocalypse and Original Scarlet Witch costumes.
First, step into the power chamber in the middle of the vault of ages. Because there is only a limited amount of time you have to use the harmonic powers, choose a faster character to do this. There is a yellow meter that will show you how much harmonic power time you have remaining. Go straight up or straight down to reach the generators. The downward path has a small maze in it. Go right instead of left. At the generator, Apocalypse is waiting. You must beat him up before you can destroy the generator. Destroy the generator and repeat the same process with the other one. It does not have a maze, and it will be a straight shot directly to it. Just like before, Apocalypse is waiting for you at the generator. After destroying the power of the harmonic machine, he will bring statues of the horsemen to life. You must focus your attacks on the horsemen and get them out of the way before tackling Apocalypse. When you kill the horsemen, they will return to statue form. Then, kill Apocalypse twice to complete the game. Note: Make sure you have a full load of health and energy packs before attempting this.
In Act 2 after you rescue Beast on Mikhails Warship, Blink will open a portal back to Avalon. Go through the portal to Avalon then immediately return to the warship. The scene of rescuing Beast will play again, and the ship is undamaged. You can go back and get all the items again. Repeat this as many times as desired.
Having two blasters (for example, Magneto) and two brawlers (for example, Wolverine) works well. The following team is highly useful, because there are times where you will need a mutant with super strength to move an object out of the way. If you need a bridge formed, use Magneto. If you need a flyer, both Magneto and Ironman can fill that role. The heavy metal group is Colossus, Juggernaut, Ironman and Magneto.