#7: Krypto The Superdog (Action Comics #583)

In the non-canon story Whatever Happened to the Man of Tomorrow?, Krypto attacked the Kryptonite Man in order to protect Superman, even though it meant certain death for himself. While he succeeded in taking down the Kryptonite Man, he lost his life soon after. Letting out an anguished moan right before keeling over, the sight of Krypto’s lifeless body is still one of the most somber in all of comics.