But he doesn't... Doomsday killed him. Magic can kill him Certain radiation can kill him. in some comic lines electricity can kill him. Kryptonite is obvious. being beaten so quickly his body can't heal will kill him(how doomsday killed him, but others can do it) phasing shit into his body can kill him.(or phasing his organs out) He can lose his powers and die. I think I missed a few also...