Successfully complete the indicated task to unlock the corresponding character:

Black Cat: Successfully complete Toyko level 1.
Blade: Successfully complete Transylvania level 2.
Doc Ock: Defeat him in Tokyo level 2.
Green goblin: Defeat him in Tokyo level 4.
Iron Fist: Successfully complete Tangaroa island Level 3.
Lizard: Successfully complete Cairo level 2.
New Goblin: Successfully complete the game.
Rhino: Defeat him in Tangaroa Island level 4.
Sandman: Defeat him in Cairo level 4.
Scorpion: Defeat him in Tangaroa island level 2.
Venom: Defeat him in Transylvania level 4.