As we get deeper into this confrontation it starts to be apparent that the only thing Russians respond to is cruelty. You have to go about it quietly, but the Ukrainian's should stop taking POWs. If there are trapped Russian forces, north of Kyiv, the Ukrainian / International forces should shell them until there is nothing left of them. If they try to surrender, just say you didn't see it and send the snipers and mortarmen after them. Drone strike infantry positions.
Whether we like it, or not, sometimes the only way to vanquish cruelty, is by matching it. They say war is hell. Make sure every single Russian knows they are in hell.
This would be the ideal time to mobilize the populations at a high level, and massacre the Russian soldiers occupying settlements. Russian lives do not matter in Ukraine right now. Take them swiftly and send them home to their mother's, in pieces.