[REQUESTING] What are the darkest, most disturbing or depressing movies you have ever seen, and what can you recommend?

Originally posted on r/MovieSuggestions on March 6, 2021. Changed list link to archive link due to the original link now being dead.

Inspired by a list from IMDb, curated by Dr. Unken (https://web.archive.org/web/20210306111226/https://www.imdb.com/list/ls031142976/), I am in search of other films that have a similar tone to the films in that list. You can recommend me anything, even if the film is the same from that list. They can be in any genre and the language can be English or a foreign language.

Examples of such films include:

• "Martyrs" (2008) (In French with English subtitles)
• "Funny Games" (1997) (In German with English subtitles)
• "Possessor" (2020)
• "We Need to Talk About Kevin" (2011)
• "You Were Never Really Here" (2017)
• "Dragged Across Concrete" (2018)
• "Green Room" (2015)
• "Manhunter" (1986)
• "Nightcrawler" (2014)
• "Kill List" (2011)
• "Enter the Void" (2009)
• "Dear Zachary: A Letter to a Son About His Father" (2008)
• "Blue Ruin" (2013)
• "Requiem for a Dream" (2000)
• "Antichrist" (2009)