Superman is notoriously difficult to kill. It's kind of his thing, and even though people have been trying to pull it off for 77 years now, they've never really managed to. Even the most famous example of someone coming close had to involve an unstoppable giant bone monster in bike shorts and a spurious understanding of evolution, and even that didn't really work --- the main result was less shuffling off this mortal coil and more hanging around for a couple of years in dire need of a haircut.
But there is one person who might have a pretty good shot. Someone who knows all of Superman's weaknesses, and who has the resources to provide a squad of hitmen with everything they'd need to put a Kryptonite nail into the Man of Steel's coffin. That man is Clark Kent, and in Len Wein, Dick Dillin and Joe Giella's "A Matter of Light and Death," which opens with Clark hiring a trio of crooks to off his own alter-ego, and just keeps getting weirder from there.