Psychological/ messed up/ twisted beyond repair

http://www.mangago.me/read-manga/litchi_hikari_club/ I suppose this would fit

OBEY ME

MADK is a great one, I'm not really into the super dark stuff, but the stylization of the artwork and intricacies of the story keep me coming back ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄

http://www.mangago.me/home/mangalist/127166/

This works wonders

The Inheritance Of Aroma might be as messed up as it gets

I recommend playing r18 BL games, especially the ones by nitrochiral cuz mmboi, they're one of a kind. There's the super popular dramatical murder but I'm talking a guy who shit out meat out of their ass and gets raped kinda thing, Sweet Pool.

Seconding MADK. Also, if you want actual messed up stuff like with no romance at all, I suggest heading over to the rape/abuse/ mindbreak tag in myreadingmanga.

some stories u can find in mangago, quite a lot are popular:
http://www.mangago.me/read-manga/tourou_no_ori/
http://www.mangago.me/read-manga/youkoso_new_world/
http://www.mangago.me/read-manga/deichuu_no_hasu/
http://www.mangago.me/read-manga/kiseki_to_amedama/
http://www.mangago.me/read-manga/chou_to_kumo_no_su/
http://www.mangago.me/read-manga/dakedo_ashita_no_hanashi_o_shiyou/

http://www.mangago.me/read-manga/i_episode_0/ +
http://www.mangago.me/read-manga/itou_san_kuraka_sui/

http://www.mangago.me/read-manga/hogu_hagyeongsu/?av=2
http://www.mangago.me/read-manga/soine_lovers/uu/tr_chapter-3/pg-1/
http://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/

there's this one i can't find. it's a one shot with a sequel. guy confessed to a girl and was publicly humiliated and for the remainder of his time in middle school he became some sorta public sex toilet, fucked up his thoughts about sex, had sex with an adult and got addicted to it. sequel has him fapping in public and a stranger found him and was gonna blackmail him by following him to his home, but the tables turned and the guy locked the stranger up and proceeded to rape him instead. moral lesson, don't follow a sick pervert to his apartment.

there's also another one, don't know if it's by harada but i don't think it is??? guy was groomed? i think by his teacher until he got raped then the cycle repeated itself at the end of the one shot

there's this other one about this guy who confessed to the mc and was watching him via binoculars from another building 24/7 which made the stressed out mc paranoid and stuff

it was straight up "Tales of the Unusual" (the webtoon haha)

http://www.mangago.me/read-manga/stalker_s_game/

I don’t know anyone who does psychologically fucked up manga better than Nakamura Asumiko
http://www.mangago.me/read-manga/coponicus_no_kokyuu/
http://www.mangago.me/read-manga/the_inheritance_of_aroma/
http://www.mangago.me/read-manga/double_mints/
http://www.mangago.me/read-manga/j_no_subete/ (Warning: suicide trigger)
And there’s also MADK, though it’s more on the gory side IMO (don’t worry that art is great) http://www.mangago.me/read-manga/madk/
And here is a little painful oneshot http://www.mangago.me/read-manga/escape_kyuugou/