10 Superheroes Who Broke Their Own Rules
5. Batman Also Kills
Batman has killed people. Not the Golden Age version, though he didn't exactly have the 'no killing' rule so it was a bit more common though. Not the films versions, such as the now-overused example of Batman blowing up one of Penguin's goons in Batman Returns, the unhinged Batman killing Joker in JLA: The Nail, the sheer insanity of Frank Miller's All-Star Batman And Robin, or whatever you infer from the ending of Batman: The Killing Joke.
Rather, starting with the Silver Age, there have been several examples of Batman killing. Ignoring those that die by indirect means, such as a mobster out for revenge against Batman being crushed by a tower of scrapped cars while firing at Bats in Batman #425 or a garbage truck dispute ending with two people being crushed in the back of one in Detective Comics #613, Batman locked the KGBeast in a room to starve to death in Batman #420.
Sure, he didn't outright kill the guy but locking a villain that had been a thorn in his side, besting him at almost every point in the story leading up to this.
In that same vein, Batman may be sadistic when he does decide to kill someone. In Batman Incorporated #2, Batman uses darts to stun the immortal Japanese villain, Lord Death Man, to put him into a veritable coffin and sends him into space to suffocate to death slowly. Truly brutal.