This may be a basic film-bro™ answer, but Oldboy is a good baseline for "kinda fucked up" but also "really really good". It's even better on the second viewing. I even recommend watching Spike Lee's misguided remake, because it makes you seriously appreciate the artistry behind what Park Chan-Wook was doing.
"Requiem for a Dream." It's a great movie to watch once. I loved it, never have any interest in watching it again, and saw the book and thought, "Oh I liked that movie I'll grab the book." I started reading, and the first scene (as in the movie) is the junkie is at his mom's place trying to steal her TV to sell to buy drugs, and she's begging him not to because she wants him to get help, and he finds she's chained the TV up so he can't steal it as he's done before, and he gets really mad at her because she's chained the TV up so he can't steal it.
I thought, "Oh, right," and put the book down immediately. I have no interest in picking it up and reading the rest of it.
Natural Born Killers. Though it really depends on threshold. Pulp Fiction is a better film imo, and some people would consider it "fucked up". But I don't really.
It's an easy answer. It's a very pulpy, violent, action film shot entirely in a real time first person vantage. A guy gets experimented on, escapes from the mad scientist, then goes on a 90 min video game quest to save his kidnapped wife. It's all explosions and train fights. It's the kind of thing you worry that people will respect you less for having enjoyed, but it's honestly an outstanding use of cinema and very fun.
Very good, but very fucked up. Hit close to home in the lifestyle I lived as a teenager, just luck that things didn't end up like they did in the movie.
A russian War Film called "Come and See"
Three hours of watching a young boy being mentally wrecked by the atrocities of War.
Gruesom, fucked up but incredible Film
A short stay in Switzerland. It's about an old lady who had a terminal illness and goes to Switzerland to end her life. It's incredibly depressing, there is a scene where she tries to suffocate herself with a plastic bag that I couldn't even watch
I don't watch a crazy amount of movies but I loved The Platform (2019). It's a horror movie and and a revolting, elegant metaphor for class inequality.
The brief synopsis below gives nothing away about how this film is so messed up.
A brilliant plastic surgeon, haunted by past tragedies, creates a type of synthetic skin that withstands any kind of damage. His guinea pig: a mysterious and volatile woman who holds the key to his obsession.
Sorry to Bother You 2018
I defy anyone to guess where that movie is heading.
The Bad Batch was pretty fantastic, and those first few minutes especially are pretty fucked. With a cast containing Jason Momoa, Keanu Reeves, and a very sneaky Jim Carey, I'm honestly surprised it didn't get more attention than it did. Maybe it's the cannibalism.
Basically, the premise is that there's this big chunk of open desert around a town called Comfort out in the middle of a fenced off area in Texas where they dump criminals. It's got a very post-apocalyptic vibe. Highly recommended.
I watched Funny Games in theaters in high school and it pissed me off so much. I literally shouted “fuck you” at a screen in a public theater. It wasn’t until much later that I realized that was the point.
"Plague dogs" is the most depressing movie I have ever seen, I was in a funk for a few weeks after seeing it. In terms of conveying an emotion no other film has lived up to that movie for me.
I think the best one had to be that remake of a Kurosawa horror film called The Grudge with Sarah Michelle Gellar. That was the only horror movie to ever actually give me a true scare.
Snowtown has been the one in my life which has really stuck with me particularly because it’s a true story. The murder scenes were so prolonged and graphic.