I often wonder what I would have done if I were in Griffith's position.
I mean, I 'know' I wouldn't sacrifice all my comrades, but then again, man. What shitty circumstances.
My thoughts about this are written as though the characters were real, living people even though I know they are works of fiction. Miura has obviously crafted very complex and interesting characters to provoke such reflection. It's not a simple question to answer, and all of the elements that comprise the fictional premise of Griffith's choice can't be fairly addressed unless you take the time to analyze all the factors.
It was unforgivable and he needs to die.
I've heard it rationalized that they were willing to die for him anyway, so there's no difference in how they died to make him stronger. This is mostly rationalization from people that like Griffith and want to somehow justify his actions.
I've always argued that they were willing to fight beside him and risk dying for him so that their dreams could ALSO be realized. They didn't just join him solely to help him become a nobleman. They also wanted their own lives to be better, and they thought Griffith would lead them all to a brighter future, one they'd all share together. This is seen when the leaders of the Band of the Hawk all become nobles after the war with Chuder ends. It's also evidenced as the 'faceless' members of the Band of the Hawk are sitting around campfires thinking about how they'll live their lives after the war is over and they've all received due rewards for their efforts. They see a future, the poor decieved bastards.
Only Guts seems wholly uncomfortable with the notion because the life of a nobleman was never what he was seeking. His dream is not the same as Griffith's. And unlike the rest of the Band's, his doesn't even run parallel to it or dovetail with it. Obligation fulfilled, he chose to strike out in pursuit of his own dream. Griffith couldn't handle that, and it broke him completely.
Granted, he was always a bastard, and willing to sacrifice anything and anybody to get what he wanted. This is driven home as the story clearly points out that only his affection for Guts ever made him stray from his purpose. Some have argued that the God Hand decieved Griffith into making that choice, but this is a a fallacy in my opinion. The God Hand wasn't deceiving him of anything. They were, through a complex series of psychological dramatizations, REMINDING him of his original focus and desire. That focus and desire which were obfuscated when Guts entered his life. This is enforced as Griffith is gestating and he sees Guts coming towards him. He's hoping Guts doesn't reach him because if he does, he'll change his mind and refuse the transformation. Only Guts could make him rethink his course of action at that point. The others don't matter.
Then there's the whole 'I'm going to have my way with Caska and force you to watch before you are both killed and eaten.' They were sacrifices, just like all the rest. They were supposed to die. Only because the Skull Knight intervened were they able to survive. Granted, there's the whole logic that Caska was his means to be reborn again at a later point and that he still has affection for Guts, but even if this is the case that still doesn't justify raping Casca when she probably would have willingly had his child, even for such a purpose, if he'd asked. It certainly doesn't justify pinning Guts down and forcing him to watch.
And all those other people that died? What, they didn't matter? If he'd warned all of them ahead of time that he'd sacrifice their souls just for the sake of his own dream if it came down to it, I'm sure less of them would have signed up. In fact, probably none of them would have signed up.
He was a scumbag from the start. True to his own dream, but trampling the lives of all others, friend and enemy alike, to get what he wanted. He needs to be maimed and kicked into the abyss so that all the people he fucked over can get their revenge on him. They're suffering eternally for his actions. So should he.
Man, it's amazing how impassioned this series makes me feel. It's one of a very few comic books I still get emotionally invested in. Pretty much this, The Walking Dead, Vagabond and Blade Of The Immortal are the only ones I care this much about. The rest are just comics.