History ThouShaltNotKill / Superman

* There were at least two [[UsefulNotes/TheBronzeAgeOfComicBooks Bronze Age]] stories in which criminals tricked Superman into believing he had accidentally killed someone, so that he would hang up his cape and stop fighting crime (in one, they tricked him into thinking he had accidentally killed ''ComicBook/LanaLang''!).

* The bylaws of the ''ComicBook/LegionOfSuperHeroes'' firmly forbid killing any sentient -- unsurprising, since they were created during UsefulNotes/{{the Silver Age|OfComicBooks}}. The tradition has been retained throughout the Legion's various continuities; even in the DarkerAndEdgier ''Legion Lost'' limited series, Live Wire officially resigned from the Legion before performing a HeroicSacrifice to kill the Progenitor, an OmnicidalManiac with [[AGodAmI the power to control matter on a cosmic scale]], in order to allow his teammates to escape without the Progenitor following them back and taking over their universe.

* The ''Franchise/{{Injustice}}'' franchise deconstructs this. With Superman being pushed to the breaking point by the Joker and murdering him out of revenge. Superman takes a hard stance against the idea of ThouShaltNotKill, believing that criminals should be dealt no mercy and executed as he pleases. He even eventually escalates to killing innocents and children, albeit as "acceptable" collateral damage.

* ''ComicBook/SupermanUpInTheSky'' turns this into the basis of a cruel moral dilemma: while on the search for a missing girl lost in space, Superman [[DealWithTheDevil ends up making a deal with Darkseid]], who pledges to help Superman on one condition: he must take an innocent life, breaking his heroic oath. Superman ends up finding an alien hermit who's in immense suffering from a fatal disease and [[DeathSeeker outright begs to be put out of his misery]], but this is still ''brutal'' for Supes as consensual MercyKill or not, he still can't bring himself to ''kill'' someone. Nevertheless, he ends up reporting back to Darkseid to confirm that the deed was done, with Darkseid satisfied that Superman had confessed to breaking his vow. [[spoiler:Turns out, however, that Supes [[TakeAThirdOption took an entirely different route]], where instead of killing or leaving the alien, he spared him by going the extra mile to find the cure for his disease to save his life (hey, Darkseid didn't ask [[ExactWords whose vow Superman broke]]).]]

''Franchise/{{Superman}}'' has taken [[ThouShaltNotKill a solemn vow never to kill]]. Moral issues aside, there's a practical reason for his oath: a demigod who had no issues with killing [[BewareTheSuperman would never be trusted]], and would be considered a demagogue, not a hero. Several alternate versions of ''ComicBook/{{Superman}}'', whether an What If? story or an alternate dimension of him, have explored a Superman who had no problems with lethal force. From a writing standpoint, keeping Superman an ActualPacifist makes it a stunning WhamShot should he actually be forced to kill, as mentioned in the very few cases where he had no alternative, and had exhausted ''all'' of the possibilities.

* It's strongly implied -- and outright used in ''ComicBook/WhateverHappenedToTheManOfTomorrow'' -- that he believes that he should give up being Superman if he takes a life. (He cannot kill himself, since his oath applies to himself as well. This was shown in a number of Bronze Age stories, including one where he is caught in a hallucination that supposedly shows the future and realizes that since it shows him killing himself, it must be false.) [[spoiler:After he kills Mr. Mxyzptlk with the Phantom Zone Projector - the latter tried to flee to the Fifth Dimension when exposed to the device, tearing him apart between the Phantom Zone and the Fifth Dimension - Superman exposes himself to Gold Kryptonite to permanently rob himself of his powers.]]