He doesn't though. He's usually pulling punches like Spider-Man. Lois Lane keeps his humanity in check, and when she dies he goes berserk. Batman's checkmate plan for this involved bringing in another Lois Lane from a different timeline/universe to talk Superman down. I want to say it was Superman: Doomsday that this all happened in. Lois dies with child and Superman goes berserk after getting attacked by Doomsday, eventually doing the classic Laser-Lobotomy.