There's no such thing as "both sides" here. It's a fundamentally flawed argument in this war. One country launched an unprovoked full scale war on a much smaller country with the goal of a colonial conquest (hopefully that's very clear by now). The amount of atrocities it has already done against Ukraine and its people will never be outweighted by pretty much anything Ukraine can do in the future as a part of its literal survival efforts.

Besides this, the laws only exist when there's something to enforce them. Has anything (apart from Ukraine's "kinetic sanctions") been enforcing much on the invader to make them obey those "laws"? At least treating POWs with dignity (like Ukraine generally does btw) and not putting them through the Gulag system that russia has revived with newfound cruelty?