“Xi is the one that will likely end this. At some point Putin’s failures will become too embarrassing for him to survive.”
China usually stays out of stuff like this. Russia has a history of long entanglements like Afghanistan but that was long ago in a different era.
I think Putin is one who ends this at a time of his choosing.
Zelenskyy could end it quicker than Putin, but he’s owned by the people that are pushing world war and has no intention of negotiating.