David Xanatos, Thailog, and Norman Osborn for starters. Morgana's proven to be quite the Magnificent Bitch as well, particularly in how she's manipulated her rapidly growing army.
Special mention should go to Roderick Kingsley. He framed Flash Thompson and Ned Lee as the Hobgoblin. He had Ned brainwashed and murdered just to fake his own death, so he could move more covertly. Had he not been unmasked in a fight, Kingsley may have even walked away with his hands clean.
Lacunae Rahdan, now a gargoyle-mutate calling herself Raksha, asserted her dillusions of superiority by eating a human being.
Viper/Madame Hydra manages to do it within an hour of being released from prison, brutally murdering both her S.H.I.E.L.D. guard and his wife and children on live television.
In addition to her moments from the show, Demona's brainwashing of Angela and her brutal and almost sexual torture of Goliath qualify. At this point, Angela has finally gotten the hint that mommy's really never coming home... although Brooklyn disputes that.
Squick: Mr. and Mrs. Osborn have a very active sex life... which he wears his mask during!