When a villain is evil, but polite. And its not an act, they are genuinely nice and polite, but won't hesitate to destroy whatever is in the way of their goal.
Pictured above is Johan from "Monster" (sorry about the image, couldn't find anything clearer), a polite, handsome, charismatic, and COMPLETELY FUCKING PSYCHOTIC young man who corrupts and kills everyone he comes into contact with for no reason.
Schneizel from "Code Geass"
Light Yagami from "Death Note"
The Mayor from "Buffy the Vampire Slayer"
Clay Davis from "The Wire"
The Mandarin from "Iron Man"
Agent Smith from "The Matrix"
Bill from "Kill Bill"
picture (c) Monster
i own none of these images nor names or movies and media