Throughout both Marvel and DC Comics, there are several superheroes who operate with no-kill policies. This means that they go to great lengths to preserve life, even the lives of their enemies. As one could imagine, this rule becomes more difficult to follow when these heroes go up against truly murderous villains.

Although these heroes take these codes seriously, there are several instances where they have broken this one rule. Whether overwhelmed by a sense of intense aggression or realistically concluding that it is the best option, there are many complicated reasons that these heroes make certain exceptions. Here are the top ten times superheroes broke their no-kill policies.

Related: 10 Superheroes Who Are Morally Questionable

10 Batman - Final Crisis

Batman Shoots Darkseid during Final Crisis

Final Crisis was an overly complicated story. As is the case with many of DC's crises. Despite this, the big event managed to be quite enjoyable for comic book fans, giving them many memorable moments.

The most notable of these moments was when Batman broke his one rule. Not only did he kill Darkseid, but he did so using a gun. This gun Batman uses shoots bullets made of Radion, a material fatal to the New Gods. Although Darkseid is able to kill Batman as well (seemingly), this is perhaps the greatest victory Bruce Wayne has ever had.

9 Iron Man - Extremis

An image of Iron Man punching through a wall in the "Extremis" storyline

One of the most iconic stories in Iron Man comics is the Extremis series. Using Extremis, a newly created rip-off of Captain America's Super Soldier Serum, a domestic terrorist named Mallen is able to give himself superhuman abilities. After acquiring these abilities, Mallen breaks into the FBI headquarters and goes on a murderous rampage.

When Iron Man arrives to save the day, it seems as though the powerful Mallen might be too much for him. Then, when it seemed there would be no way to stop him, Stark used his repulsor tech to blow the villain's head clean off.

Related: 10 Iron Man Armors We Hope To See More Of In The Comics

8 Daredevil - Shadowland

During the Shadowland crossover event, Daredevil became the leader of the evil ninja clan known as the Hand. Eventually, it was revealed that his erratic behavior was due to the fact he was being possessed by a terrible demon. While he was under the influence of the said demon, Matt crossed many lines he never would have dreamed of crossing before.

One of these lines was murder. After stopping his long-time arch-nemesis Bullseye, DD sought a more permanent solution to this criminal threat. Much in the same way that Bullseye had murdered Elektra, Daredevil stabbed the assassin through the stomach with a sai.

7 Spider-Man - Spider-Man Versus Wolverine

Spider-Man vs Wolverine. Logan holds Charlie in his arms as she dies.

In one of Spider-Man's many adventures, he teamed up with the mutant Wolverine to rescue a woman named Charlie. Having previously worked for the KGB, Charlie knew too much and was a liability that needed to be removed. As it became clearer that she would never be able to outrun her past, Charlie decided she wanted to die.

After asking Wolverine to kill her, Spider-Man got involved, hoping to stop the hero from crossing that line. As the two heroes fought and Spider-Man's spider-sense became overwhelmed. By sneaking up behind him, Chalie tricked Spidey into thinking she was Wolverine. He then threw a super-powered punch, killing her. Both Wolverine and Spidey knew Charlie essentially committed suicide-by-Spider-Man, but that didn't stop Spider-Man from feeling massive amounts of guilt.

RELATED: Spider-Man: 10 Things You Didn't Know About Peter Parker's Parents

6 Superman - Trinity War

Recently recruited to the JLA, Doctor Light didn't last on the team for very long. Losing control of his powers, the newly admitted league member accidentally attacked Wonder Woman. Wonder Woman was dating Superman at the time, and this attack apparently sent him over the edge. Despite Doctor Light profusely apologizing, Superman used his laser vision to decapitate the superhero.

This erratic behavior was later explained. Superman had apparently been implanted with a piece of kryptonite behind his optic nerves, allowing a villain to control the Man of Steel's actions.

5 Wonder Woman - Sacrifice

Wonder Woman Breaks Maxwell Lord's Neck

Although she is known as an Amazonian warrior, Wonder Woman was notable for refraining from killing her enemies during her stint with the Justice League. This ceased to be the case once Maxwell Lord entered the picture.

Using his telepathy to control Superman, Lord was manipulating Superman into killing all superhumans. Realizing the only way to break Lord's control of Clark would be to kill the villain, she ferociously snaps his neck.

Related: DC: 10 Worst Things Wonder Woman Has Ever Done

4 Flash - The Slayer and The Slain

Barry Kills Reverse-Flash

The Reverse-Flash's mission in life is to make Barry Allen suffer. Over the course of his history, Reverse-Flash has killed many of Flash's loved ones.

When Thawne decided to kill Barry's wife on their wedding day, the Flash felt like he had no other choice but to kill his arch-enemy. Chasing Thawne down at superspeed, Flash grabbed the villain's neck and quickly decelerated, snapping it and killing Thawne.

3 Batman - The Dark Knight Returns Part Two

Batman and the Joker's corpse in Miller's Dark Knight Returns in DC Comics

After Batman's resurgence in The Dark Knight Returns, Joker decides to come out of retirement as well. Chasing Joker through some fairgrounds, Batman is unable to stop the supervillain from gunning down several innocent civilians.

Deciding the Joker was simply too dangerous to be left alive, Batman breaks the clown's neck. Bruce admits that he should have done so sooner, having felt responsible for every death the Joker had caused.

Related: 10 Most Dangerous (But Least Physically Impressive) Batman Villains In DC History

2 Superman - Injustice: Gods Among Us

injustice-joker

In the Injustice: God's Among us story from the popular video game of the same name, the Joker decided to target Superman instead of his traditional enemy of Batman. Tricking the Man of Steel into killing his own pregnant wife, Joker hurt Clark in a way that no one else ever has.

Pushed to the absolute brink, Superman had had enough of the mad clown. He then punched a hole straight through Joker, instantly killing him.

1 Daredevil - Born Again

Born Again is by far the most iconic Daredevil story. Written by Frank Miller, the dark and gritty tale takes Matt Murdock to many very dark places, truly pushing him to the limit. Towards the end of the story, the supervillain Nuke.

While perpetrating a mass shooting rampage in the middle of Hell's Kitchen, Nike received support in the form of a helicopter. Gunfire from the helicopter was killing multiple civilians on the ground, leaving DD with few options. Picking up Nuke's large machine gun, Daredevil shot down the helicopter, saving many innocent lives.

Next: 10 Best Daredevil Storylines In Marvel Comics, Ranked