ONE FLEW OVER THE CUCKOO'S NEST (1975)

Nicholson performance in this film has been voted as the best performance by an actor of all time

One Flew Over the Cuckoo's Nest is one of the greatest American films of all time; directed by Milos Forman, film is based on Ken Kesey's 1962 best-selling novel.
Set up in the world of an authentic mental hospital (Oregon State Hospital in Salem, Oregon), the story is about defiance against the Establishment and institutional authority by an energetic, rebellious, anti-hero character, played by Jack Nicholson.

It was the first film since "It Happened One Night" (1934) to win all five of the top Academy Awards, for best picture, actor (Nicholson), actress (Louise Fletcher), director (Milos Forman) and screenplay (Lawrence Hauben and Bo Goldman).

Randle Patrick McMurphy (Jack Nicholson) has served two months of his six-month sentence and has managed to get himself transferred to the state mental hospital for psychiatric observation, figuring that life in the loony bin would be easier than on the prison farm.

But the martinet Nurse Ratched (Louise Fletcher) runs the psychiatric ward with an iron fist, keeping her patients intimidated through manipulation, abuse, medication and sessions of electroconvulsive therapy.

"Nicholson slips into the role of Randle with such easy grace that it's difficult to remember him in any other film"

"Is "One Flew Over the Cuckoo's Nest" not a great film because it is manipulative, or is it great because it is so superbly manipulative? I can see it through either filter. It remains enduringly popular as an anti-establishment parable, but achieves its success by deliberately choosing to use the mental patients as comic caricatures. This decision leads to the fishing trip, which is at once the most popular, and the most false, scene in the movie. It is McMurphy's great joyous thumb in the eye to Ratched and her kind, but the energy of the sequence cannot disguise the unease and confusion of men who, in many cases, have no idea where they are, or why."

https://www.rogerebert.com/reviews/great-movie-one-flew-over-the-cuckoos-nest-1975