Griffith shouldn't have let it get to him when Guts left.
He was about to be made a noble, he had eliminated all his court rivals before they could do the same to him, and a princess had a crush on him. He was a few short steps away from becoming king and fulfilling his dream.
But when he loses Guts, he can't stand the idea of one of his followers giving up his dream, and is to selfish to comprehend that Guts wants to be his friend, not his servant. So he throws a tantrum, has sex with the princess before becoming a noble and marrying her, which in turn causes the king to go bonkers incest crazy, beat him up and have him tortured and mutilated to the brink of death.
It's his fault. Griffith's tragic flaw of pride and ambition leads him to become a broken shell of a man, and lose his dream. Until of course he gets it back by sacrificing his friends to demons...
