Superheroes: Spider-man, Batman, Moon Knight, Captain America, The Ghost Rider, The Punisher, and Wolverine. Don't have just one favorite.
Villains: The Joker, Sabretooth, Green Goblin, Venom, Carnage, Darkseid, Omega Red, and Crimson Dynamo. Same as before, not just one.
Mercenary: Deadpool hands down.