Doomsday is the only one in main comics continuity to ever kill Superman; and he did so simply by beating the man of steel to death. Doomsday was killed in the battle, as well, but later healed himself and returned to life, stronger than before. Superman has encountered him on numerous occasions since.

Can Superman permanently die?

While Superman has died before on several occasions, he's never stayed that way for long. ... Prime Earth Superman perishes in The New 52 storyline The Final Days of Superman, while Lex Luthor uses a Kryptonite spear to do in the Man of Steel in the tie-in to the DC Universe Online Legends video game.

Can Superman only be killed by Kryptonite?

Even non-comic readers know that Superman is susceptible to Kryptonite. But that's not the only thing that can take out the Man of Steel for good. Absorbing man because he can just absorb kryptonite and he will be superman's superman. ... Kal-El has such a sterling reputation that most people think he's invulnerable.