Cat from Zelazny's Eye of Cat. Also Billy Singer's Chindi from the same book. As antagonists, Cat who has lost everything just wants one last chance to be himself and hunts Billy and I totally get that. He's lost everything and due to his current predicament as being a zoo exhibit, has been forced to be different than what he knows he would have been, had he been left alone. I really feel for him, right up to the end. The Chindi because well, there really are few things worse than fighting yourself, especially the part that you've run away from your whole life. As someone who figuratively has to battle with things my past self has done, I like Chindi because well, I know what it's about. Thank god I don't have to actually fight a real literal version of what I run away from though.
Fenris from Norse Mythology. Yes he'll destroy all of creation when he's set free, but perhaps if he, oh you know, would have actually had parents that disciplined him as a child, then perhaps he wouldn't bring about the apocalypse. I feel for this guy because he is a product of his environment. Everything bad he will do or has done can be tied to other people f*****g up with raising him and they act like it's not their fault. If I could, I would punch Loki, Tyr, Odin, and the dwarves, and numerous other Norse deities in the face for what they've done to Fenris to allow him to get out of hand.
I also like Fenris from A. Lee Martinez's Chasing the Moon. Especially in how he leaves our layer of reality at the end after Diana gives him a good talking to. All it took was someone to talk to him, someone who gave a damn.
Megamind. Because Presentation.