Magnificent Bastard - Marc Remillard, to a point. Sometimes he seems quite reasonable and gentlemanly and charismatic, but let's not forget he caused the deaths of four billion people, turned his son into a fish, and is STILL trying to find another world to take over to use for his Mental Man scheme- might I add that this involves creating a civilization of bodiless brains?
Aiken Drum is also a Magnificent Bastard, at least as far as the Tanu are concerned - he outplays them and the Firvulag at almost every turn. Marc beats him only because he's older and better at the game.
Woobie, Destroyer of Worlds - Felice; YMMV somewhat on how much of a woobie she is. But for a certainty, bad things happened to her and tipped her into raving insanity (and power).