I suppose GER could use its near-limitless Stand energy to create a lifeform that could digest Kars after he smashes him to pieces with a Muda Muda rush, but it still seems a bit contrived when it was outright stated that neither lava nor the freezing temperatures of space could kill Kars and that he literally was incapable of aging or dying.Even if he can't, I'm sure Giorno could find a way to defeat Kars just like Joseph did.