Vader imo he's gone out of his way to kill anyone and anything for his own selfish goals and self.loathing.
Injustice Clark isn't much better but imo the worst thing he's done is kill Billy. Vader has slaughterd or aided in thr slaughter of countless children and even worlds simply because he was told to. Ij Clark at the very least does still care for others and can feel remorse such as saying sorry to Hal when giving him the news his city and family were gone.
Vader. He's such a petty, selfish character. And he's stupid. He went out of his way to kill five year olds because the emperor said it would make him stronger with the dark side. How is he that dumb? And then he tried to murder his wife, which is the whole reason he turned evil