The first idea that comes to mind is a guy who is tough but has a sense of humor. Even if he's tied up, I'm inclined to play him as always considering her an equal. Maybe he'd taunt her the whole time.
Hmm. As for whether or not he was innocent of wrongdoing or committed some of the atrocities.. I think something less black and white. Maybe it's nothing personal- he's just a mercenary.. Hmmm