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?
“What a fool you are. I’m a god. How can you kill a god? What a grand and intoxicating innocence. How could you be so naive? There is no escape. No Recall or Intervention can work in this place. Come. Lay down your weapons. It is not too late for my mercy.” - Dagoth Ur in Morrowind