Cannibal Holocaust
This found-footage drama has been routinely banned from a long list of nations for it's graphic and violent portrayals of cannibalism. This film crew gets lost in the Amazon and witness a tribe amidst their ritual exchanges. It was so intense to viewers that many believed the actors from the film were thought to have been killed on set.
The Strangers
Make sure you wear your mask for this film. A couple with issues brewing shows up at a cozy house in the forest, but their trip gets interrupted by a group of masked strangers. The violence would be brutal under normal circumstances, but the senselessness makes it so much harder to watch.