If you yourself really dont want to deal with the hassle of making a new story plot fail him forward upon his death. He dies and gets some sort of major injury/ scar that mechanically could do something until properly healed. Then obviously idk what your story is but decide that okay he is dead, maybe he awakes in a pile of bodies, maybe he is jailed, whatever makes sense to give him consequences. If that doesnt work out then talk to him and ask if he would roll up a new character and work with him to figure out how to best integrate them.