I just watched "Marriage, Not Dating", and I'm currently watching "High Society".  It just so happens that both have such messed up characters with no morals that it's hard to watch some times.  I'm really curious about more of these types of shows with love "hexagons" (instead of triangles), corruption and infidelity.    

Our Gap Soon was so frustrating some of the characters were so out there. Also Daily dramas have ridiculous plots and often a cheating spouse for either the lead or a close relative of the main characters as a side story. Not quite a hexagon though.
Maybe try Go Ho's Starry night it was reverse harem with an exboyfriend as 2nd male lead, main lead is a boss with an unrequited love for female lead and there are other guys confessing their interest for her too. 

Any drama that has assault in it, ESPECIALLY if the assault is overlooked and diluted into a forgotten mistake, and not something that speaks to the utter lack of humanity in a person. Besides that, the usual makjang elements of dailies and certain longer dramas are always pretty messed up (like horrible parents trying to control every aspect of their childrens' lives thus making them miserable...can extend to anything from marriage to murder). Sometimes you see a window into how deeply patriarchal society still is and how women, despite how they are as individuals, are genuinely treated as nothing but child-bearers and maids is horridly frustrating, and just as much unfair. I think one specific example that stands out among others in my early drama watching (re: just a lot of messed up elements) was Que Sera Sera, like, was all that happened really necessary lmao? Also anything fauxcesty that borders a little bit too much on the -cest part.

Cruel Romance. Couldn't finish it because it just felt so wrong. ML was so domineering over the FL and she allowed him to be??? That part that made me drop it- the ML was horny af but the FL wasn't ready for sex and he just pushed for it. Huang Xiaoming's good looks can't even save his trashy character. Smh.

Kuzu no Honkai was messed up, all the characters were mentally unstable people

Atami no Sousakan is pretty messed up, but in a good way. 

I agree with Kuzu no Honkai, like seriously I put it on hold because I cannot take it. Even when Dori is there. haha

Black for me. Lots of loopholes actually.

The great Seducer, they have no moral,

The Heirs : they are so arrogants and so full of themselves. The dominance of the wealthy social class is bothering.

Creating destiny: I don't know if I'm the only one but the main girl's family was so racist, there were so many cliches about foreign people. What's more, the female lead had no moral, she kinda cheated on her "american" boyfriend and was very not respectful. Still, the chemistry of the main couple was great, no wonder they got married in real life.

i love my president though he’s a psycho that drama is just so weird couldn’t finish it like wtf 


Kuzu no Honkai was messed up, all the characters were mentally unstable people

After watching that I felt every single character needed to go sit down and speak with a psychotherapist. I was just in complete awe at how messed up every single one was.

Anata no Koto wa Sore Hodo- talk about not being able to root for ANY of the characters. Even the husband who was cheated on lol dude was a freakin psycho and the wife was the trashiest person I ever did see.

Boku no Yabai Tsuma- I wouldn't wish this marriage on my worst enemy (but the drama itself was damn good)

Le Jun Kai- As the above commenter stated with violence towards ladies, this one was hella violent. The way the ML treats the FL is really reprehensible. Its a short drama (9 epi each being less than 20 min long) and it took me a while to finish and I had to watch something light to recover.

Le Jun Kai, Sealed With A Kiss and I have a lover

In both Le Jun Kai and Sealed with a kiss ML is violent towards FL. It's disturbing at times. 

I Have A Lover is the most messed up story I've ever watched. Especially the first 9 episodes are frustrating. But it's a good watch. Loved it by the end. 

This Thai BL called Together With Me(prequel) and Bad Romance. Lord it's getting a 3rd season and I don't know why.

The lead guy is a legit asshole and their relationship is only built on sex. They fight about petty shit, bringing their best friend in to solve their problems but god forbid that they actually talk. Haven't seen them have a serious conversation ever. Total toxic relationship. 

✔️ Alice: Boy from Wonderland 

They had amazing hot chemistry and then they drop a majorly sick twist at the end that you can't accept  

SPOILER... they only met when he was a baby and she is a few years older and they are half siblings who meet again in a parallel universe as adults... He originally died as a baby) 

suspicious partner