I'm looking for some dramas where the main character is the bad guy or at the very least does things that are considered bad. 

I've seen: Flower of evil, Mouse Extracurricular, Smile has left your eyes, Strangers from hell, Kill it, Bad guys, Heartless City, My Name.

Thank you

My Mister.    The FL commits several crimes and probably should have gone to prison for a while.     

In That Winter The Wind Blows  the ML is a con man who pretends to be somebody else.  

In the early episodes of Chief Kim, the ML is either committing fraud or skirting dangerously close to doing so.  

But probably the worst is in Chicago Typewriter, where the ML in his earlier life in the Resistance randomly shoots into a crowd at a party, murdering innocent people  in the process. 

So if you are interested from people going from good to very very bad than i would highly recommend you 2 chinese dramas;
Burning Ice
The Bad Kids
Both are very very good.

Another one that is not as good but also follows this trope is this chinese drama;
Kidnapping Game


Then korean dramas where the lead is considered to be a murderer;
Defendant 
Missing 9 

Considered to be a murderer and does bad things;
Lie of a Lie  (korean)
Train (korean)
Kill it (korean)
My name (korean)
Aku no Hado (jp drama)
Forgotten (korean movie, but fits this topic also very very well)
 
Less serious shows;
Psychopath Diary (korean)

hi, I have list exactly of what you want, I even didn't added "Flower of evil" (great drama btw) because for real ML wasn't bad at all, I think he even was great person who didn't becomes bad no matter of all events in his difficult life. so check this out:

https://mydramalist.com/list/32AwQNYL


also Cruel City (heartless city) is my favorite drama and if anyone knows something even close to it please recommend <3

I don't have hope to see equally good drama because I thought several times "it's like Cruel City" but after few episodes was dissapointed 

 hayaka:
worst is in Chicago Typewriter

it's really good drama but ML never was considered as bad, I didn't even remembered that scene, it's kind of war time... I don't know, as character he was never shown as anti hero or bad, he was even kind of hero in previous life

  • The Devil Judge
  • Punch
  • Cheese in the trap
  • Dr. Prisoner
  • 38 Task Force
  • Bad Guys
  • Lucifer