You got it backwards. You've never read the book, I take it. That's OK. It's common for people who watched the movie as kids years ago to mistake McMurphy for a hero and Nurse for a "heartless tyrant".
McMurphy is an immature idiot trouble maker. McMurphy ends up lobotomized then dead. That's not a good thing.
Nurse Rached tries to keep the loonies under control. Nurse Rached wins in the end.
Chief is the hero.