I know some people here are desensitized to many forms of violence or related things in fiction. When 11-12 years old talk openly about seeing movies like Hostel, Saw or the Texas Chainsaw Massacre, there is not too many secrets anymore and the shock factor in films isn’t what it would have been 20 years ago or earlier.
However, I wanted to discuss movies that you may have found tough to watch because of their delicate topics or their story ( not because they were bad!). For example, Schindler’s List was a great film but it was difficult to watch because it showed the reality of the death camps.
I have seen the following two movies and I think they qualify as great films I found very difficult to watch because of their topics. They are not for everyone ( people who liked the films listed in the first paragraph would find these boring for sure), but those who like different kinds of film will like these for their great artistic qualities despite them being tough to watch.
Edit: I realized I didn’t finish my sentence.