Servalan is the best villainess in the history of ever. (points to icon)

She's from "Blake's 7". Initially she's the head of the Space Force of the evil Federation. Apparently the military dress code doesn't apply to her, because she goes everywhere in evening gowns. She swims the waters of politics like a shark, smiling and smiling and being a villain. She also uses feminine wiles whenever it suits her. She definitely would have been a Slytherin.