Recommendation for manga with male/female protagonist who start off as normal/good person but later face moral conflicts and start going to the darker side.

Example : unordinary
munou na nana

Bump.

Akame Ga Kiru might fit what you're looking for. 😁

The main protagonist originally starts out as a typical shounen dude, naive and idealistic. Until he finds out the capital is beyond corrupt and eventually joins the side of assassins who take out people like cruel politicians.

Thank you for our encounter~

Azumi might not completely fit your criteria but it's a good manga
My Home Hero this has breaking bad vibes going, I've read a few chapters so I can't tell entirely
Zankoku na Kami ga Shihaisuru read this only if you have a strong heart, it's extremely depressing. It's Delimma The Manga
Kirihito Sanka if you like classics