Looking for good disturbing films

I'm looking for disturbing films NOT in the vein of a Serbian Film, Human Centipede 2 etc, shock value horror, more like films that explore dark parts of humanity in an interesting and engaging way (regardless of genre). I've heard of/watched/am planning to watch the most famous ones so I would appreciate some not as well known suggestions. Thanks!! (side note, I don't have a big issue with explicit scenes, I just don't want the films to be explicit scene after explicit scene for the sake of it)