Batman's war on crime in Gotham has sent him to some pretty hardcore places. The Dark Knight has no problem being as violent as possible, but there are certain rules that he follows. The biggest one is that Batman doesn't kill. Now, this rule is mostly just in the comics, and even then it depends on the universe or the time in the Caped Crusader's life. However, the mainline Batman does everything he can to avoid killing and has been known to go after heroes who violate his rules.
Source：https://www.cbr.com/batman-no-kill-rule-dc-comics-origin/
