@Black_Panther_JS did you watch the anime or the movie?
In the anime they show what happened to the world after griffith took over all the way back in the first episode. It became a living hell for 99% of the humans in the kingdom
With regards to guts, Griffith tried to straight up kill him (even when he didn't need more sacrifices so he just wanted him dead) and also branded him with a mark
That makes demons chase after him and hunt him
24/7
And Casca completely lost it for over a year in berserk time iirc after what happened.
All this because griffith got himself locked up and GUTS saved him. He saw guts & casca living well and had to act like a scorned hoe
I get that a year of being tortured to the point of losing your tongue & the ability to talk would completely change you as a person and the griffith before that and the griffith after are basically different people. It's like the whole people who are bullied becoming bullies dynamic. At some level he also acknowledged that in war people were risking their life for him at some point and it got to his head, giving him a god-complex.
The fact that it seems plausible for griffith to do that is good writing but its all ultimately a
for him being a peice of shyt in general and a TERRIBLE friend