If somebody's character does not die, then nobodies really trying.
It is at that point that the DM must decide if an act of God(s) need to happen to change the flow of fate.
I once had a character ripped in half by my own party members. They were actually trying to save me, they did not know that I was being held in a turtle dragons mouth when the guy with storm giants strength was pulling me out of the water. BUT, as I was wearing a ring of regeneration I was allowed to grow my lower body back. I even had almost all my toes when it was done.