As for the first part of your comment, no. Being in the official military of a country is not a crime or entering into a criminal conspiracy, so if a soldier goes rogue and decides to do something they shouldn't, that's only on them. However, if a commanding officer orders a war crime, and it's carried out, then yes, everyone in the chain of command below that, and is associated with the war crime, is a war criminal. Like, say, the US pentagon ordering drone strikes on a hospital. Just trace metaphorical lines from the people that ordered it, and their subordinates, and theirs, all the way down to the people who did the actual act. Everyone that touches that tree is a war criminal. In fact, under the laws of war, soldiers have a legal duty to actively refuse any order they know to be a war crime, and it's a separate war crime to punish a soldier for refusing to commit the original war crime. "I was just following orders" is very explicitly not a defense, IIRC this was actually passed internationally after too many Nazis used that line.

Also, an official national military is a special case where most civilian laws don't apply, that's why we have military law and military courts. But the same is not said for a paramilitary organisation like the Azov.