TBH I'm not even sure that the succubus paladin is legal. I know that at least some of those Fight Club monsters were illegal. I'm honestly not sure how to look at knifing her. I doubt even the force that granted her power would be quite sure how to call that one. In the other 99.999999% of cases I personally think that the fiend ganking wins. Even with D&D's absolutist alignment system some things are gray.