Peter wanted out but stayed. Again and again.
Again and again, he covered for and saved Carrie. He went against his training, his superiors… He didn’t care for Brody, but he supported her through it all. Even with all his debilitations his main priority was keeping Carrie and her child safe, even dying for a mission she took upon herself and something she believed in.
Peter Quinn managed to stay coherent during one of the biggest character developments. Surely the biggest in Homeland.