Just wanted to share a theory about how Berserk will end.

Guts will probably do something to the God Hand that will change them back to there human form, including Griffith, and Skull Knight will probably help him. This way he could actually kill them. Imagine Griffith would be like at the end of the Golden Age Arc again, like right after he was saved from the tower. But since Guts has to pretty much decide between killing Griffith, or kinda forgive him, which would kill his rage for the most part, I think he will choose the second thing, so he won't kill Griffith. Instead he will keep Griffith somewhere at the place he resides in at the end of the story (like in a locked basement or something) and will keep him alive. This would be a bigger revenge than actually killing him, because Griffith would know that Guts is living a happy life together with Casca now, and there's nothing he can do about it, plus Guts finally lets go of Griffith and his revenge.