It's hard to choose any to pick out, especially as it's now been a couple of months since I finished my first playthrough; but there just aren't really any bad characters in the game. The ones I dislike are purely because my character didn't get on with them - like, I stabbed Astarion in the gut when he tried to bite me after making snide comments every time I wasn't a dick to someone. But you can bet in my next, evil playthrough, he's going to be in the party.
But pretty much everyone in this game is an interesting, well-acted character in their own way, whether that's an origin character through the whole game to a bit player in a side room.
