There are quite a few severely disturbing films out there. These films are so disturbing that even the description of them can traumatize some people. Please do not read the descriptions if you think you might be traumatized by reading about them; you can just read the titles and general descriptions and know that they are probably not for you.
I've created a comprehensive list of what these films are, the content of these films, and my thoughts on them. I personally haven't seen some of these films because I believe that they would cause secondary traumatization. However, I have read enough about the ones I haven't seen to determine their content and why they are considered the most disturbing films of all time. This list will contain minor spoilers so as to explain the film content.
1. A Serbian Film (2010). This film follows an ex-pornography star who is drawn into a world of illegal pornography and snuff films.
Why is it so disturbing?: The film depicts several graphic scenes of child sexual abuse and rape (young children and babies), necrophilia, human suffering, gore, and extreme violence.
My thoughts: I have never seen this film and never intend to. Reading about this film on Wikipedia is bad enough, and I don't recommend it to anyone for any reason. I don't understand how something this horrible could ever be made and it makes me sick to think of all the people that were involved in this film and continue to watch it.
2. Martyrs (2008). This film follows two girls named Anna and Lucie who had been tortured as children by a society of people who seek information about the afterlife.
Why is it so disturbing?: The film depicts several disturbing scenes of graphic bloody torture, extreme and graphic violence, body horror, human suffering, gore, murder, and suicide. One of the most disturbing scenes is when a woman is skinned alive and lives through it.
My thoughts: I haven't seen this film either. I don't like to watch films containing torture or extreme violence, and this film seems to have no redeeming value for me. I understand that some films may contain violence to evoke feelings of empathy, compassion, and sadness, but this film seems to only evoke feelings of disgust, shock, and repulsion. This film was remade in the United States and released in 2015.
3. Irreversible (2002). This film follows the story of a woman who has been through extreme trauma and the events that preceded the attack.
Why is it so disturbing?: This film depicts a nine-minute scene of rape and violence against a woman. Although not extremely graphic, many define this film as extremely disturbing and difficult to watch.
My thoughts: I haven't seen this film because I'm not into watching rape scenes period, much less nine-minute rape scenes. I can sort of understand why the director stayed with the actors and made the rape scene so long if it was because he wanted the audience to really empathize with the character. It's one thing to imply a brutal rape, and quite another to show it for the entire time. Although I understand the reason for the scene, I still won't watch this movie; it's just not for me.
4. The Skin I Live In (2011). This film follows a plastic surgeon who is keeping a woman captive at his estate.
Why is it so disturbing?: This film depicts a man named Vicente who is kidnapped, then forced to have gender reassignment surgery against his will. Vicente is forced to live at an estate by another man named Robert, who blames Vicente for the seeming rape of his daughter (which didn't actually happen) and her subsequent suicide. As a punishment, Robert uses experimental plastic surgery to mold Vicente into the image of his dead wife, Vera, who committed suicide many years earlier. Vicente is later raped by Robert's brother, then almost raped by Robert.
My thoughts: I have seen this movie. At the time, I had no idea what the movie was about and watched it without knowing what was going to happen. I wish I had researched it, because it is a very disturbing film. I can't imagine being kidnapped for some perceived crime, then forced to become another gender against my will. It seems like anyone would lose their mind after that happened to them, and I remember being truly shocked when I learned what happened to Vicente.
5. Hostel (2005) and Hostel II (2007). These films depict travelers in Europe who fall prey to a club of people who pay to torture them for sport.
Why is it so disturbing?: This film depicts several scenes of extreme violence, graphic torture, human suffering, murder, and gore. One of the most disturbing scenes in the first movie is when it depicts the intense, graphic torture of the victims in the various rooms. Each scene is very disturbing and gory. One of the most disturbing scenes in the second film is when a girl is hung upside down, naked over a bathtub. A woman sits in the bathtub and takes scythe and cuts the girl's back so as to bathe in her blood. She then cuts the girl's throat to kill her.
My thoughts: I have seen both of these films and regret it. I love horror films, and when I was younger I used to be able to watch films that bothered me. Now I protect myself from disturbing content because I know I am sensitive to it. I wouldn't recommend these films to anyone who can't handle graphic violence, human suffering, torture, and gore.
6. Salo, or the 120 Days of Sodom (1975). This film follows a group of young men and women who are kidnapped, tortured, and raped for 120 days.
Why is it so disturbing?: This film depicts several scenes of extreme violence, torture, rape, humiliation, human suffering, murder, suicide, disturbing verbal stories, and scenes where people are forced to eat human feces.
My thoughts: I have never seen this film. I can't believe this kind of film exists, but if this kind of film can be made, it's no wonder movies like A Serbian Film can be made. I would never watch this, nor would I recommend it to anyone. I fail to see any redeeming qualities about this film.
These are the most extreme movies I have come across in my research. There are many disturbing films out there, but these are the ones I have seen over and over again in my research. If you think these films sound disturbing, below I have included a list of other disturbing films I suggest you avoid as well.
Antichrist (2009) (Denmark) - body horror, graphic sex scenes involving violence, female castration
Raw (2016) (France-Belgium) - violence, gore, cannibalism, body horror
High Tension (2003) (France) - violence, gore
Deadgirl (2008) (United States) - rape, violence
A Clockwork Orange (1971) (United States) - torture, rape, violence
The Human Centipede (2009) (Holland) (avoid both sequels as well) - body horror
The Exorcist (1973) (United States) - religious slurs, demonic activity, violence, murder
The Last House on the Left (1972) (United States) - rape, violence, murder
Black Swan (2010) (United States) - gore, body horror
Requiem for a Dream (2000) (United States) - body horror
mother! (2017) (United States) - murder, graphic violence, violence against children
Oldboy (2003) (South Korea) - incest, torture, violence, attempted suicide
Ichi the Killer (2001) (Japan) - torture, violence, murder, rape, gore
Audition (1999) (Japan) - violence, torture
Begotten (1990) (United States) - rape, violence, religious slurs, anti-religious themes
Cannibal Holocaust (1980) (Italy) - torture, rape, murder, gore, violence, cannibalism
Inside (2007) (France) -torture, violence, gore
I Spit on Your Grave (1978) (United States) - rape, violence, murder
Black Christmas (2006) (United States) - incest, rape, violence, murder, gore
Deliverance (1972) (United States) - rape, murder, violence
Wolf Creek (2002) (Australia) - rape, murder, torture, gore, violence
Evil Dead (2013) (United States) - graphic violence, gore, rape, demonic themes, body horror, murder, self-mutilation
The Texas Chainsaw Massacre: The Beginning (2006) (United States) - torture, graphic violence, rape, gore, body horror, cannibalism
The Loved Ones (2009) (Australia) - torture, gore, graphic violence, self-mutilation, body horror, cannibalism
Backcountry (2014) (United States) - graphic violence, gore, body horror
The Exorcism of Emily Rose (2005) (United States) - violence, demonic themes
Hellraiser (1987) (United States) - torture, graphic violence, body horror, gore
Halloween II (2009) (United States) - graphic violence, murder, gore, body horror, violence against animals
Hard Candy (2005) (United States) - pedophilia, violence, suicide, murder, body horror
Saw (2004) (United States) - graphic violence, torture, suicide, murder, body horror (all of the Saw movies include the same kind of material)
The Fly (1986) (United States) - violence, body horror, gore
Cabin Fever (2002) (United States) - violence, body horror, murder, gore
Slither (2006) (United States) - body horror, graphic violence, gore, murder
Starry Eyes (2014) (United States) - body horror, graphic violence, gore, murder, demonic themes
American Mary (2012) (Canada) - body horror, violence, gore, rape
This is not an all-inclusive list, but these are films that I have either seen or know to be disturbing. I hope that you find this list helpful. If you have any questions, please feel free to ask.