The two most disturbing films I have ever seen are:
I have seen many films in my life, but two stand out that were so disturbing they caused me depression and they caused me to question the existence of god and goodness in the universe.
1) the first movie that caused me trauma was "Banned in America". This was a rough shot documentary that featured real life death torture and mutilation from around the world. This film is what Faces of Death claimed to be, except it was real. I suffered from nightmares, depression, and post traumatic stress disorder after seeing the film. I eventually had to see a therapist.
2) the 2nd movie was The Cat in The Hat