KAKISTOS. BtVS Demon/Monster/Villain.
An ancient (he has hooves rather than feet) and powerful demon who comes to Sunnydale ("Faith, Hope, and Trick") accompanied by Mr. Trick in search of Faith, having previously killed her Watcher.
Buffy has difficulty with his name:
GILES: The, um, vampires that attacked you, can you furnish me with some details that might help me trace their lineage? I mean, ancient or-or-or modern dress. Amulets, cultish tattoos...
BUFFY: Uh, no tats. Crappy dressers. And, uh... Oh, the one that nearly bit me mentioned something about kissing toast. He lived for kissing toast.
GILES: You mean 'Kakistos'?
BUFFY: Maybe it was taquitos. Maybe he lived for taquitos. What?
BUFFY: Is that bad?
GILES: 'Kakistos' is Greek. It means the worst of the worst.
In a final showdown with the Slayers, he is killed by Faith (staked with a very large piece of wood).