Few comic characters are as elastic as Batman, but one of the fairly ironclad components of the Caped Crusader's characterization is his rule against killing. Whether it be because he's afraid of what he'd become if he embraced more violent methods or if he just believes in the human capacity for redemption, Batman abhors lethal action.

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That's not to say he's never been tempted, though. Batman has one of the most erratic and violent rogues galleries in superhero comics, and many (especially the Joker) have frequently brought him to the brink of murdering them.

10 A Death In The Family

A Death In The Family Stare-Off

Batman's greatest failure remains failing to save Jason Todd, the 2nd Robin, from being murdered by the Joker. Occurring in Part 2 of the four-chapter "A Death in The Family," by Jim Starlin & Jim Aparo, Batman decides to assuage the guilt over his adopted son's death by killing the Joker. Unfortunately, the Joker has recently been named Iranian ambassador to the UN (a misguided attempt to infuse contemporary politics into this story published in 1988) and so had diplomatic immunity. Even when the Joker loses that by attempting to blow up the UN, the clown still manages to escape Batman's wrath.

9 Under The Red Hood

Batman Joker Under The Red Hood

After Jason returns to life, he becomes a lethal vigilante using the Joker's original costumed name: Red Hood. Jason's motives are only fully revealed in the story's climax, after he has abducted the Joker and lured Batman to an abandoned apartment. There, he tells Bruce that his anger is because Bruce failed to kill the Joker to avenge him; now, he wants Bruce to rectify the mistake. Batman admits he fantasizes about killing the clown everyday, and is sorely tempted to finally make those thoughts reality. To Jason's frustration, Batman can't bring himself to do it, too afraid that he'd be crossing a line he couldn't venture back across.

8 Heart Of Hush

Heart of Hush Batman Kicks Scarecrow

This time it wasn't the Joker on the receiving end of Batman's wrath (though he did have a front-row seat from his Arkham cell); rather, it was the Scarecrow. After Hush surgically removes Catwoman's heart as a twisted gift to Batman, Bruce tracks down Hush's partner-in-crime, Jonathan Crane. In one of the most brutal interrogations he's ever performed, Batman seems inches away from killing Crane. Ironically enough, the Joker egging Batman on is probably the only thing which made Batman stay his hand, for it would've reminded why he has his rule in the first place.

7 Superman/Batman: Supergirl

Batman Darkseid Apokolips

In the Superman/Batman arc which reintroduced Supergirl/Kara Zor-El, Darkseid captured her, intent on adding the young Kryptonian girl to his collection of Female Furies. Aware of the damage Darkseid will wreak if he's allowed to keep Kara as a servant, Batman threatens to use Darkseid's own Hell-Spores to blow up Apokolips.

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Though enraged, Darkseid ultimately concedes, seeing that Batman isn't bluffing. After releasing Kara, he admits grudging respect for Batman's willingness to cross a line most of his heroic compatriots wouldn't have been.

6 The Dark Knight

The-Dark-Knight-Batman-and-Joker

The Joker spends most of The Dark Knight trying to get Batman to break his rule against killing, all part of a greater scheme to prove the feebleness of rules in general. The closest he gets is in one of the movie's most famous scenes, where after he's imprisoned, Batman interrogates him to learn the captured Harvey Dent's location. The clown finally cracks Batman's armor by revealing he also had Rachel Dawes kidnapped; unbeknownst to the Joker, she's not just Harvey Dent's girlfriend, but Bruce Wayne's childhood love and the one Batman's stoked his hopes of a normal life on. When the Joker says Batman will have to break his rule by choosing one of the two to save, Batman doesn't argue the Joker's point, but just says he's considering breaking his rule there and then.

5 Hush

Joker Hush

In "Batman: Hush," the Dark Knight stumbles upon the Joker standing over the seemingly dead body of his childhood friend, Thomas Elliot. Though the Joker protests that, this one time, he's innocent, Batman doesn't care. He begins pummeling the villain to pulp – he's about to deliver the killing blow when Jim Gordon arrives on the scene, talking Batman down by reminding him that if he kills the Joker, then Gordon will be the one bringing him in.

4 The War Of Jokes And Riddles

Batman with blood on his hands in the War Of Jokes And Riddles

In "The War Of Jokes And Riddles," Batman tells Catwoman a dark chapter from his early days of wearing the cowl – one where the Joker and the Riddler competed for the right to kill him. Throughout the retelling, Batman hints at a secret which has haunted since the events of the flashback. This shameful secret is revealed to be that he tried to murder the Riddler, and was fully in control of his faculties when he did so; he was only stopped when the Joker took the hit and, being the Joker, survived.

3 "Chill Of The Night!"

Chill Of The Night

In Batman #47, a story written and drawn by Batman's creators Bill Finger & Bob Kane, Batman confronts the man who killed his parents, Joe Chill. Furiously revealing his true identity to Chill, now an aged mob boss, Batman is clearly just holding himself back from taking lethal vengeance.

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Bruce doesn't get the chance, however; after running away in fear, Chill tells his henchmen of the role he played in Batman's creation (without mentioning the Caped Crusader's true name). For that revelation, the thugs gun their boss down. This story, with much of the climax unaltered, was adapted as Batman: The Brave and The Bold episode "Chill Of The Night!"

2 Batman Beyond: Return Of The Joker

I'll break you in two

Return Of The Joker famously features a flashback scene depicting the final confrontation between the DCAU Batman and Joker. What the Joker does to Robin in this sequence might eclipse "A Death In The Family" as the worst fate to ever befall the Boy Wonder. Tim Drake is abducted by the Joker & Harley Quinn, who spend three weeks torturing and brainwashing him into "JJ," their grotesque vision of a son. Inviting Batman to an abandoned Arkham so he can see the results, the Dark Knight's horror mutates to rage at the sight of his deformed ward.

Batman fully intends to kill the Joker, but the clown unfortunately gets the upper hand with a surprise knife attack. When Joker tosses a spear gun to the brainwashed Robin, telling him to kill the limp Batman, the former Boy Wonder's original self breaks through, and he shoots not Batman, but the Joker. As Tim breaks down in tears, Batman can only look on in remorse at what fate he led the boy towards.

1 The Dark Knight Returns

TDKR Batman Chokes Joker

In Chapter 3 of The Dark Knight Returns, an aged Batman has resolved to finally kill the Joker – "the list of the people [he's] murdered by letting [the Joker] live" has simply grown too long. When the moment comes, and Batman has the Joker's neck in his grasp, he holds himself back by his teeth and twists just enough to induce paralysis.

In keeping with Frank Miller's depiction of the Joker, the crippled clown mocks Batman for holding back as if the Dark Knight's gone impotent. Like most are inclined to do when their partner can't bring the fun to its climax, the Joker finishes the job himself; he twists his neck until it fully snaps, going out with a devilish laugh.

NEXT: Dark Knight Returns: Every Member Of The Bat Family's Fate