10. Spider-Man 2/3
Harry Osborn is the typical oveer-achieving best friend type to Peter Parker. He's handsome, rich, popular and athletic - basically the opposite of Peter's traditional image - and yet he's undoubtedly an entirely wholesome character. After all, he chooses to be Peter's friend when others might balk at him being a bit of a dweeb.
He lives in the shadow of his father, but he is initially far from the corporate wunderkind archetype.
When Norman Osborn is killed, Harry is unable to forget Spider-Man's part in it, vowing revenge and using Doc Ock (and then his own guise as the second Goblin) to try and kill him. And when he discovers that Spidey is his best friend it flips a switch that turns him into a full-blown bad guy, despite initially helping Peter take down Octavius.
He ends up getting his redemption in the end, but for a while there, Harry was definitely a monster.