One Flew Over the Cuckoo’s Nest(1975)

Winner of 5 Oscars – Best Picture, Best Director, Best Actor (Jack Nicholson), Best Actress (Louise Fletcher), Best Adapted Screenplay.

POOPER: (Thanks Curt, THE GRAND POOP-BAH)
Chief Bromden (Will Sampson), understanding his true wishes, suffocates the lobotomized McMurphy (Jack Nicholson) with a pillow, and escapes the hospital by throwing a sink through the window.

Longer version
The electroshock therapy punishment imposed on McMurphy by Nurse Ratched (Louise Fletcher), far from affecting or subduing him, makes him even more determined to stand to her and encourage his fellow patients to do so. He plans, along with Chief -who happens to not be deaf or mute, having just faked it all along-, to throw a huge Christmas party at the ward, behind the backs of Ratched and the staff, prior to their intended escape from the institution. He even goes as far as bribing the night shift guard orderly Turkle (Scathman Crothers) to allow it to happen without them being ratted out.

That night, McMurphy sneaks his girlfriend Candy (Mews Small) and her friend Rose (Louisa Moritz) into the ward through one of the windows, them both carrying liquor. Everyone feels liberated and has a raucous good time; meanwhile, McMurphy tries to convince young Billy (Brad Dourif) to join him and Chief in going away, but Billy, basically feeling like a man-child and having been institutionalized for a better part of his life, is afraid of leaving, although he does beg McMurphy to let him “have a date with Candy” -that is, to lose his virginity to her-, to which they all agree, thus Candy and Billy retrieving to one of the rooms to spend the night together.

Instead of leaving with Chief, McMurphy gets caught up in the moment and ends up getting drunk with everyone else and passing out in the middle of the floor. The next morning, Ratched arrives and, to her dismay, finds everyone scattered all over the place and a huge mess; she commands the staff to clean up and herd the patients. Moreover, she discovers the room where Billy was in bed with Candy -to which everyone cheers lively- and, in her usual condescending way, admonishes him for his actions. Despite the fact that, seeing his confidence boosted and his stutter apparently gone from the experience, Billy attempts to stand up to her, Ratched gains the upper hand by threatening to tell his mother, an old friend of hers; this unravels Billy, causing him to stutter again and have a meltdown, while Ratched orders to isolate him in another room as part of his “punishment”.

Now determined to escape the institution, McMurphy prepares to fight with Washington (Nathan George) for it, having punched another one of the orderlies while attempting to flee through the same window with Chief, when, suddenly, a blood-curdling scream from a distraught nurse catches everyone’s attention: Billy committed suicide while locked away. Amidst everyone’s shock and rage, Ratched indifferently commands the normal continuation of everyone’s daily routine; this causes an enraged McMurphy to jump her and almost strangle her to death, which doesn’t happen because he is knocked unconscious and pulled off and away from her.

Some time later, things seem to go back to the usual, robotically-directed ways. Ratched is seen wearing a neck and speaking in a hoarse, visibly affected voice as a result of the attack, but barely having changed her ways nonetheless. Harding (William Redfield), in absence of McMurphy, has taken over the card game, which now goes on non-stop. Everyone speculates he might have actually been able to escape; however, that night, Chief catches a glimpse of McMurphy being returned to his bed. Initially rejoicing to see his friend back, he then realizes with sadness, upon seeing a huge scar on his forehead, that McMurphy was lobotomized.

Chief tearfully hugs McMurphy and, understanding he is now doomed to die in that place anyway and intending to honour their joint promise, mercifully kills him by smothering him with a pillow and then tears the hydrotherapy console off the ground and smashes it against a window -something McMurphy swore he would eventually do, earlier in the movie-. As Chief runs off into the night, Taber (Christopher Lloyd) and some other inmates witness it and celebrate.