For me, it would be GLaDOS.
Portal 2 spoiler
She deleted the one remaining human part of herself because it was just too much to deal with. She releases you at the end of Portal 2 as a path of least resistance measure because “killing you is hard.”
What about you, what is your favorite media villain?
Sand dan Glokta from the First Law series of gritty fantasy novels by Joe Abercrombie.
He is a crippled, razor-tongued former war hero turned inquisitor: physically ruined by torture but mentally sharp, cynical, and ruthlessly pragmatic.