Finish Chapter 1.
Finish Chapter 1 with Black Cat without changing hero. (1-Player only)
Finish Chapter 2.
Finish Chapter 2 with Hawkeye without changing hero. (1-Player only)
Finish Chapter 3 with Namor without changing hero. (1-Player only)
Finish Chapter 3.
Finish Chapter 4 with Spider-Man without changing hero. (1-Player only)
Finish the game.
Finish all levels without changing hero. (1-Player only)