There are pretty harsh rules against killing unarmed POW’s. They actually get enforced when it’s possible (not often enough) to positively identify the perps and catch them. It’s usually some years later, of course.
Both sides have soldiers who behaving ‘unethically’. I’m just stating facts. I have a solution, how about Zelensky go to the negotiating table with a Putin. I know Zelensky wrote a law stating it was illegal to do so. But, he can rip it up and be a big boy and do what needs to be done so that more of his soldiers aren’t killed. It’s Hard for me to have any other opinion on the matter until he does this.