Let's see, the joker? No. Golb? No. Bill cypher? Good choice, but no. As stupid as this answer might be, for me, it's most likely homelander from the boys. Homeland is established to be a cruel, terrifying, and sociopathic villain who doesn't care about who lives or dies, and all though that can be said about the ither villans I had listed, homelander is diffrent. For an example, the joker kidnapped Jason Todd, tortures him, and became the ultimate reason red hood even kills, but homelander doesn't kill people to hurt someone else, he just kills because he likes it. The joker does everything he does to get closer to batman to mess with him, but homelander just wants to see blood. Another example, Bill Cypher torments Ford and uses the people of gravity falls as his puppets, but he does that because he felt restricted by his realms 2 dimensions and wanted to be a God. Homelander thinks he is God, and thus believes he can just do anything he wants, a decides not to commit mass genocide, but torment people one at a time and either convince them to kill themselves or kills them because he's done toying with them.