Snape. I also write Snape. And much like Loki, that slimy, amoral bastard isn't even remotely honest with himself much less anyone else. I also write a lot of Azula, but I wouldn't call her a favorite. More like a compulsion with a flame thrower.

Zuko has a lot of problems similar to dishonesty associated with writing him, as he's spectacularly unself-aware for most of the show.