Superman is the best superhero in the world, and he will never die unless you put like a lot of kryptonite to him and he will fall to the ground and probably die from all of it. So therefore superman can’t really die unless you have like weird space rock from space and get close enough to him to either stab him or just put it up to his skin. I’m pretty sure no one would want to kill superman because who would hate superman. Unless your like Lex luther and you just really want to kill superman because you’re a freak and is jealous because superman has super powers and you don’t.