My problem wasn't about Batman actions being justifiable or not.
The thing that bothered me is the way Tom King tries to mantain the "no kill" rule without actually sticking to it. If KGBeast died in that situation, that would be considered murder just as much as if Batman had shot KGBeast with a gun. In fact, Batman rendering KGBeast totally incapacitated to die in the snow is more cruel.
It somehow makes it seem like Batman follows the "no kill" rule, because he wants to torture his enemies