Warmaisach
I personally wouldn't mind a dark and sad ending to this story. It would actually feel pretty fitting. If he never is redeemed and after killing the God just suffers for eternity by fighting as a mindless beast until he reaches the peak and finds nothing left to fight. Then he takes his sword and kills himself because he can't handle doing nothing. And then the novel ends like that or similar to that. Not every story has to have a happy ending. I'm not even sure what a happy ending for this novel would look like at this point.