Belos. No question. Unlike the Core, Belos has complete control over his actions and takes sincere pleasure in the atrocities he commits, whereas the Cores morality and actions are completely dictated by Aldrich and the rest of the Leviathan clan. Plus, Belos's crimes are much more personally cruel than the Cores, and his character hits much closer to home for anyone who's ever been a victim of a religious zealot and/or cult leader like him.
