All he ever did was try to do the right thing and generally his reward was watching the people he loved get killed or people he trusted rise to power and betray him/leave him in the dust.

I’m not saying what he did was OK, but that bitterness festered over a very long period and over many events. Not to mention this all started with the genocide of the human race, which I imagine is going to take a bit of a mental toll on someone lol