Drama's with toxic romantic relationships?

• Extracurricular 
• Secret
• I picked up a star from the road
• It's Okay not to be Okay (light toxic relationship) 
• Moon Lovers

 Abby:

The main couple is toxic or shoulf i say hero is toxic and that part is top notch! My fav lol on other part basically other plot i totally skipped it lol. I only watched the part where woon tak was obsessing over heroine. 

Thank youu I'll def watch it :)

 Meg:

Yes the ML and FL's parts are the only ones worth watching. He is so obsessive! 

Another one is Love in Sadness, both male leads in this are obsessive in their own way.

You can also try  The Last Empress ,  I am not sure whether it's 100% what you are looking for, because they focus more on revenge than romance, but it has a very unhealthy dynamic, especially when it comes to one of the male leads.  Beware part of the summary is a bit deceiving, I would even say not true.

Ohh i have watched the last empress and i really liked it!  It was a surprise for me bcs i wasn't expecting it to take that route but that made it better.  I haven't seen love in sadness tho. So I'll check that out too