Norman was his name. And he was definitely creepy.
Hank Scorpio. Actually creepy in the"yeah my next door neighbor was such a nice guy, how was I supposed to know he wanted to rule the world?" way. Plus he kept raw sugar in his pockets.
Linda Fiorentino’s character in “The Last Seduction”?
Heh, the Gentlemen from Buffy get my vote for most creepifying villians. It was the scene where they went into the guy’s dorm room and went at him with a scalpel (all while smiling politely), and because they had stolen everyones’ voices, the guy couldn’t even scream! :eek: :eek:
Jubal is another good 'un, because of how outwardly calm he is, even though you can see in a couple of shots (the “River’s in their head” shots from that episode) that he’s just totally flipping out, grabbing his head and screaming, etc. Also, the references River made to stuff Jubal did to the dog :eek:
Looking to Babylon 5, I would have to say my favorite one-off villian from that show was Sebastian, if only because I can sympathise with any character being asked an important question that they don’t know how to answer (really, any college student can relate to that situation 
). Also, the revelation at the end of the episode and his little monologue was suitably chilling. The sandwich interrogator in the 4th season ep where Sheridan is a POW is in second place, though of course all one-off villians on B5 are nothing compared to Psi-Cop Alfred Bester and Mr. Morden, both of whom recur in big ways.
Frank Zucco from Due South would get the vote if he didn’t show up again in a second episode of the show.