When Batman holds a gun, it just looks wrong to us. There’s no hard evidence of when exactly it was decided that Batman would be against guns and killing, but in his early appearances in the comics, he was still evolving as a character and used to carry around a gun, plugging gangsters like other pulp heroes of the time did. Superman? He’s killed. So has Hawkeye. And Spider-Man. And Captain America. Below is a list, focusing on the characters who have been adapted into film and TV shows as our starting point. If it’s popular, we’ll do another list down the road.
It wasn’t long, but in Batman’s first year of stories he would sometimes kill his enemies. To be fair, he seemed to regret it. But in his early appearances he carried a handgun and would shoot his enemies. The above panel is from Batman #1 (1940) just one year after debuting in Detective Comics #27. He first guns down some men, saying he regrets it. He doesn’t seem to regret hanging this guy too much, though. He also impaled dudes and crushed them with his car in those early issues. But by issue #4, when using a gun, an editorial note said that Batman never shoots to kill and never misses.
In Superman Vol 2 #22 (1988) Superman murders three Kryptonians, Zod and two of his followers. He knows exactly what he’s doing, too. Technically it’s a parallel world where several Kryptonians survived but Superman argues that they’ve killed everyone on Earth and they deserve to be punished. So he exposes them all to Kryptonite. It drove him a little bonkers for a while, but yeah. Superman killed.
Captain America was a soldier in WW2 so I’m not counting that. That’s war. But once he started his career as a superhero, he’s made the tough decision to kill. While Steve Rogers does not carry a handgun, in Captain America #321 (1986), he is forced to gun down an ULTIMATUM terrorist or innocent people would be killed. The weird thing is Steve thinks to himself that he’s NEVER killed before. But that’s a retcon, because in Captain America Comics #3 (1941) he straight up murders a retarded man by impaling him with a dinosaur bone.
What, you think I’m making up the retarded part? No, I wish I was. Here’s where that doomed man was introduced, who is referred to in the story as “an imbecile”:
In Iron Man #229, Iron Man is on his crusade to shut down all other powered armor based on his designs, from the Armor Wars story arc. He battles the Soviet opponents Crimson Dynamo and Titanium Man (worn by another villain, The Gremlin, instead of the usual wearer Boris Bullski). During their fight, Iron Man’s jet boots eventually ignite Titanium Man’s armor and once titanium starts burning, you really can’t stop it. So Gremlin burns alive. The West Coast Avengers kick him off the team for his actions.
In Siege #4 (2015) superhero Sentry kills Thor’s brother, Loki. Actually, it’s a little deeper than that. Sentry has a dark side, Void, who was allowing Sentry to be controlled by the evil Norman Osborn who attacked Asgard. Sentry killed Ares and other heroes. Loki was able to revive them in a last act at redemption. But the end result was Thor attacking Sentry. Ultimately, Sentry wants to lose because otherwise Void would take over. Thor snaps the dude’s neck. Brutal.
There’s a lot of heroes whose villains die by accident, a victim of their own machinations. But for some reason, when it happened to Hawkeye, the Avengers judged this instance a lot more harshly. In Avengers #229 (1983) the villain Egghead had a plan to kill Hank Pym fall apart but picked up his gun to shoot him in the back. Hawkeye shot an arrow down the barrel which caused the energy gun to explode and kill Egghead. Accident, right? Well, Hawkeye never misses. He’s cleared by the Avengers but essentially on probation.
Justice League villain Prometheus is basically an evil Batman. He takes out the entire team and cuts off Arsenal’s arm (Green Arrow’s former sidekick). He detonates bombs which kill Arsenal’s daughter and threatens to set off more unless the JLA allow him to leave which they grudgingly do. But Green Arrow sneaks into his base and shoots him dead with a regular old arrow in Justice League: Cry for Justice #7 (2010).
Flash’s enemy Professor Zoom threatened to kill Flash’s second fiancée, Fiona Webb on their wedding day in Flash #324 (1983). Zoom had already killed Barry’s first wife, Iris. This led to a chase around the world and moments before Zoom could kill Webb, Barry Allen put Zoom in a chokehold. But since they were moving so fast it led to snapping his neck and killing him. Whoopsie doopsie. Things got very weird after that with Flash convicted in court, Webb losing her mind and Barry travelling to the 30th century where he was reunited with his reincarnated wife, Iris. Then DC rebooted all their titles.
Criminal mastermind Max Lord believes superheroes are too dangerous to allow and he mentally controls Superman, using him to beat Batman. Threatening to kill others, Wonder Woman places Lord in her lasso of truth and commands Lord to say how to stop Superman (The OMAC Project, 2005). Lord replies “kill me” so Wonder Woman does. A killer Superman was just too great a threat. The footage was recorded and broadcast to the world, ruining Wonder Woman’s reputation. Batman and Superman shun her for her actions.