Umm, Grey Worm was like that. WAS. Then a woman who loved him taught him he can be more and can live a full life. He started to change, no longer be a war machine. Then all that was taken away from him in an instant. ... Damn right he is hungry for revenge at the whole world now. Who wouldn't be? I am sorry but you are referring some spinoff book. Was he ever in the TV show in the past 7 seasons? If not, why did you expect a deus ex machina?