10 Superheroes Who Broke Their Own Rules
1. Superman Kills Mr. Myxzptlk
Truth, Justice and the American Way! That is a staple tagline for the big blue boy scout, and what's more American than murder? Okay, so that may have been too dark of a rhetorical question but yes, even the Man of Steel has fallen victim to breaking the Golden Rule.
Superman has killed a few people in his time, such as executing a pocket dimension General Zod and his allies with green kryptonite, though he does feel bad about it. The far more infamous moment of Superman reaching a breaking point is during the Our Worlds At War story where, to save the universe, he sends Imperiex and Brainiac back to the Big Bang and have them blown up that way.
He also shattered the Cyborg Superman, Hank Henshaw, into tiny pieces to reclaim his mantle as Superman during the Return of Superman part of the Death of Superman mega-storyline. Henshaw is a cyborg so it isn't exactly clear if that counts as killing him or not.
The biggest, however, is in Alan Moore's "Whatever Happened To The Caped Crusader". Mister Myxzptlk has grown bored of being an annoyance to Superman and starts killing off key people in Superman's life. Superman retaliates by trying to send him to the Phantom Zone but inadvertently rips him in half, killing him.
Why is this the biggest? Because it is the last Silver Age Superman story, and by the end, Clark Kent depowers himself in guilt. It may not be the most brutal death Superman has caused, but it had the biggest impact.