LOEY

You're probably already reading this: Kiss The Scumbag.
If you're okay with novels, I really recommend: Professional Body Double.
Manhua(also adapted from novel but imo manhua doesn't do the novel justice): Borrowed Hearts. Ex-husband Wants to Marry Again.

I JUST REMEMBERED, I should try to sell these to you:
Professional Body Double: MC is a stunt double, is in a FWB domestic relationship with ML, but ML actually likes MC's Actor who he's a stunt double for. MC unfortunately dies filming a documentary, and finds himself in the body of someone who has the exact name as him a few years later.
Today I learn: There's a Thai drama adaptation, here's the trailer: https://youtu.be/9lzKraOt4dk

I forgot to mention another novel: Turns Out I'm Crazy
ML - actually he's the protagonist, so technically he's the MC - ends up indirectly killing Shou/Uke iirc, MC dies soon after. MC was such a horrible person as a form of karma he finds himself in the past and in Shou's body and now he has to deal with a younger him.

Toxic Affair
ML tells MC have been in a relationship for years, but because of family duties he will be marrying a woman, oh but they can still be together. MC nopes out of that. ML chases after him and forgets the last few years (which was when they knew each other and got into a relationship). ML doesn't get why they're in a relationship, MC is so bland. "Oh, but why do I get so bothered when you're out of my sight?" type of thing.

Borrowed Hearts: MC and ML have been in a relationship for years, but all of MLs friends were horrible to MC and kept saying ML actually cares about ML childhood friend and he's just a substitute because the childhood friend is too sickly. MC gives ML the ultimatum: to stand up for MC and prioritise him for once instead of the childhood friend. ML doesn't take this seriously, scoffs, "I'll see you went you come crawling back in 2 weeks." Two weeks later the ML was called to identify the corpse of MC.
If you're okay with choppy translation: Borrowed Hearts is also is listed as Substitute Relationship.

Ex-husband Wants to Marry Again
ML(α) and MC(α) are in a relationship, but then ML turns MC into an omega by drug, "how else can I marry you unless you're an omega??" MC does everything he can to leave, but ML is the type who would cripple the MC to keep him from escaping. Honestly, this one is actually quite frustrating; it's a world where there are no morals and ethics, only money and power. There was 1 too many forged medical documents, I went "ML, at least twice we had doctors signing documents falsely, in fact, you managed to buy one yourself! Why would you trust _any_ of these doctors reports?"

OMGGG THANK YOU SO MUCH YOU'RE A LIFESAVER!!ヾ(☆▽☆)

Maybe Perfume The Memory, this still just on my To Read list, but it looks like it follows the basic premise of:
>ML and MC are in a relationship for at least a couple years
>ML treats MC badly or takes MC for granted
>MC leaves
>ML goes: Babe, wait! I'm sorry, let me make it up to you! orz
This soap opera type of drama is my junk food. But I don't think in Perfume The Memory the MC leaves.

Although I paused reading Heavy Rain novel, it does an exceptionally good job on MC being depressed and not forgiving ML for what he did imo.

If you want Angst and not borderline melodrama I just remembered these two manhwa:
Beyond the Memories
MC is an omega, arranged marriage with ML, deja vu?

Into The Rose Garden
MC loves ML, ML marries MC's cousin. MC gets jealous and indirectly kills the cousin. ML treats MC really,
really horribly.

Please let me know if any of these are hits or misses.

Thank you so much, really! I've read quite a bunch of them already actually, and imo all of them were an absolute hit. But that's just my opinion because I really love plots and dynamics like this!