Successfully complete the indicated task to unlock the corresponding character:

Deadpool: Successfully complete the Washington D.C. level. 
Green Goblin: Defeat Green Goblin and Venom at the end of Wakanda: Act 3. 
Hulk: Collect all five Gamma Regulators. 
Iron Fist: Choose the Rebel side. 
Jean Grey: Collect all five M'Kraan Shards. 
Luke Cage: Select Anti-reg when given the choice, or get him after Iron Man 
grants amnesty to the Anti-reg. 
Ms. Marvel: Successfully complete the New York City level. 
Nick Fury: Successfully complete the game. 
Penance: Defeat him in the portal room to the Negative Zone. 
Reed Richards: Select Pro-reg when given the choice, or get him after Iron Man 
grants amnesty to Anti-reg. 
Songbird: Choose the Register side. 
Thor: Collect all five Asgardian Runes. 
Venom: Defeat Green Goblin and Venom at the end of Wakanda: Act 3.