I can mostly only help you with the tragic bl side of things lol (I avoid red flag stories like the plague)
Oh and fyi, most of these stories aren’t finished, so I don’t know if they have a happy ending or not. Even if they do, they’re already tragedy-coded soooo
Oh and the hearts stand for their hair colors (notice how there’s so many yellows and blacks? Because those couples ALWAYS have at least ONE who was abused as a child in some way or is simply traumatized)
https://www.mangago.me/read-manga/the_unjust/ One such example of a story that I don’t know if it’s a tragedy or not
I have some pretty difficult ones to stomach, I don’t know if they’re exactly what you’re looking for though. Most of them are really smutty.
https://www.mangago.me/read-manga/gintama_dj_mienai_kusari/ (abusive)
https://www.mangago.me/read-manga/poison_and_sex/ (abusive)
https://www.mangago.me/read-manga/sex_cam_d/ (abusive)
https://www.mangago.me/read-manga/uruwashiki_shuen/ (tragic)
https://www.mangago.me/read-manga/a_second_goodbye_to_you/ (Psychological)
https://www.mangago.me/read-manga/sweet_heart_trigger/ (Toxic)
https://www.mangago.me/read-manga/akuheki/ (Abusive

If anyone has recommendations for this niche, I'd really appreciate it.
Some I've read or plan to read:
Gl -
Destroy It All And Love Me In Hell
I Love Your Cruddy
Weakness
Of Flowers And Unmet Promises
Bl-
Sadistic Beauty Bl Sidestory
Color Recipe (and other Harada works)
Unchanged Man
The Summer Hikaru Died
Killing Stalking (not technically bl whatever)
(+ some elements of Hiro Haruyoshi's works, even though they're not "relationship" centered)
Others in my tbr list:
Oyasumi Punpun
MADK
Fatale Game
Inside Mari
Home Far Away
Boy Meets Maria
Blood On The Tracks
Reverse Thinking and Non Zero Sum might be a bit too much for me to stomach, but I think that's because the plot has been pretty stagnant and repetitive (and full of porn) so I'll give them some time