Warning! Spoilers for Batman: Curse of the White Knight #8
Batman's biggest rule is that he doesn't kill people. It's part of his moral code and has led to numerous conflicts within his own Bat-Family. However, in Batman: Curse of the White Knight, Batman scrapped the code in order to put down a villain for good - and he seemingly succeeded, killing Azrael.
Sean Murphy and Matt Hollingsworth Batman: Curse of the White Knight has put Bruce Wayne and Batman in an all-new light. While the first White Knight arc began with a cured Joker trying to make Batman the villain, Curse of the White Knight took further aim at Batman's identity. In the story, it's revealed Batman isn't a Wayne, as Azrael is really part of the Wayne bloodline. Azrael has sought vengeance on Batman - killing Jim Gordon, while nearly killing Batgirl. It's all caused Batman to reveal his real identity to the world, give away his fortune, and for him to go on one last mission before turning himself into the Gotham City PD: Kill Azrael and than put an end to his Batman persona.
Batman and Azrael have a fiery confrontation in Batman: Curse of the White Knight #8. After a chase where a plane explodes and Batman tries to kill Azrael with a machine gun, the villain corners him and says "there won't be a city left, not after the flood..." before Nightwing hits him with his car. Azrael plans on taking out the dam at the Gotham Reservoir. Batman and Nightwing share a heart-to-heart before Bruce goes after Azrael again. After catching up with Azrael at the dam, Batman brings out rapiers and tells him they should fight with his sword since it "is God's will."
The two spar before falling onto a batmobile floating in the water. Azrael loses his sword to Batman and with little defense left, he asks Batman whether his parents knew about the true history of the Wayne family: "Did they know they were swine draped in pearls? Leeches feeding from the bloody tit of Gotham. Fake aristocrats from a rotten bloodline. An enraged Batman slits Azrael's throat in a shocking moment. The two have one last moment before Azrael seemingly bleeds out - although, it's not confirmed he died. Batman: Curse of the White Knight ends with Batman turning himself into prison and that his fortune will be dispersed across Gotham. Batman knew the repercussions of killing Azrael and revealing his identity. Now, he's got to pay for them. It's a fitting end to a great arc that proved unafraid to shake up Batman's core story and beliefs.