Books where ML suffers from his mistakes.

I am really REALLY sorry if this is too specific. What I am looking for is a book where the main character is a man who once does a mistakes and suffers from it later in his life, not like in he gets arrested and collectively bashed by people but it ruins his life and most importantly his mental health, he loses his mind (or comes close to it, or gets PTSD from it). And the mistake is not something like "oh poor guy got into horrible circumstances and had no other choice" or others forced him. He did it, but not mistankenly, maybe he had no bad intentions and he thought nothing could go bad, but it does, and anytime he tries to fix thing it gets worse, much worser that imaginable, he does this to himself. Roskolnikov and Dr. Frankenstein are kinda close to what I am looking for, but the closest is Edward Elric from FMA (2003), if anyone here watched that anime, pls recommend me something similar to the morally gray character developmet of Edward Elric in this Adaptation. Again I am sorry if this is too specific. I'd prefer if the ML is an adult and No SA in the story. Thanks for bearing with me, not a native English speaker.