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?
Blaine from iZombie. He’s 100% bastard, and the show tries to humanise him by showing us origins and “how could he be any different” and so on, but he’s always great on screen.