Films which disturbed you?

[JaseSF]

The Last House on the Left (1972)
Monster (2003)
The Texas Chain Saw Massacre (1973)
Albert Fish: In Sin He Found Salvation (2007)
Requiem for a Dream (2000)
Freaks (1932)
Threads (1984)
Happiness (1998)
The Exorcist (1973)
Se7en (1995)
The Wizard of Gore (1970)
A Clockwork Orange (1971)
Naked Lunch (1990)
Hobo with a Shotgun (2011)
Spanking the Monkey (1994)
Kissed (1996)
Straw Dogs (1971)
Léolo (1992)
Ma Mère (2004)

[Archivist]

Two that I've mentioned before:

Xiu Xiu - The Sent Down Girl (1998).  Directed by Joan Chen, it follows the story of a 15 year old Chinese girl sent to live and work in the country by the Maoist government during the Cultural Revolution.  She yearns to go back to the city, and she begins sleeping with local officials in hopes they can send her back. 

Meanwhile, the farmer with whom she is staying is in love with her, and watches silently as a literal procession of men use her night after night.  She becomes pregnant, has an abortion, and realizes that she has been used and will never see the city again.  She asks the farmer to kill her, and bury her in the rock pool he made for her.  I found that movie so disturbing that it kept me awake all night, and I had to talk about it with work colleagues the next day. (Indy gave me karma after I talked about how that movie affected me the first time. Thank you, Indy.)

https://en.wikipedia.org/wiki/Xiu_Xiu:_The_Sent_Down_Girl

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Santa Sangre (Sacred Blood) (1989).  Alejandro Jodorowsky (The Holy Mountain) directs a crazy movie about the life of a boy who grows up in a circus of freaks.  Tattooed women, armless people, random knife throwers, delirious cults and messianic imagery abound.  The trailer for this movie played when I went on my first date with my first girlfriend (we saw Almodovar's Tie Me Up, Tie Me Down, a super date movie!), but I never saw Santa Sangre until maybe eight years later.  So glad I didn't see it as a teenager, it would have messed me up even more than I already was!

https://en.wikipedia.org/wiki/Santa_Sangre

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[indianasmith]

Something about BULLY bothered me tremendously.
I think it was the complete and utter moral depravity of every single character in the film.