Well, Albedo owns he's one of my favorite enimies. I wish you could play as Negredo (can't remember his other name lol) I don't know who the best enemy would be, there's just so many. My favorites

Achilles (Ender's Saga by Orsen Scott Card)- A young man you has this crazy mental disorder, in which he has an uncontrollable urge to kill anyone that sees him in a helpless state, even if the people are triing to help him.

That's all I can really think of...