I went with the Home World's Porre General. If he was going to torture Riddle and set off some killer Robot on the party, then he is sadistic, and fiendish, and especially since we can't see him!
Azala isn't really fiendish. He was more going insane. When he realised that the humans were going to beat him, he forgot about it and thought that well if the Reptites go, then so will the humans. But that didn't happen anyway.
Daltan is just like Ozzy, Pure comic relief. He isn't insane, but really pissed off and thinks he's great.
Ozzy: See above. But he's also stupid too.
Queen Zeal isn't a bad person. After the death of her husband, all she could do was harness magic. Sometime along the way, Lavos influinced her and she wanted to be Immortal, through him. She wanted it, it was her goal, and she wouldn't stop. She doesn't seem to sadistic, maybe fiendish, but it's not her fault.
Lynx is under FATE's control, which means he's being controlled by a psycho Mother Brain series. Though he should be more lethal, he's not. Not very sadistic, but more operative to get the mission complete.