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?
Sir Captain Becket of the E I C
Dart Maul (from a german movie called (T)Raumschiff Suprise)
Bill Cypher
The villains of the Kings Men