It can also be dramas with a detective that works in unconventional way, like skirting on the edge of the law to conning people to get evidence. Some dramas I’ve watched like this are:

- Two Cops (This one is a bit of both)

- The Good Detective 

- 38 Task Force

- Memorist

Ohh grey characters, i like them as a theme too. These are some dramas with detectives that fit your request;
Watcher
Burning Ice - 12 episode cdrama.
Day and Night - 24 episode cdrama
Beyond Evil 

Some other characters that are also fitting the bill but dont work as detectives;
Devil Judge
Money Flower


xxmai Volunteer Staff
 thatkiddownthestreet:

It can also be dramas with a detective that works in unconventional way, like skirting on the edge of the law to conning people to get evidence. Some dramas I’ve watched like this are:

- Two Cops (This one is a bit of both)

- The Good Detective 

- 38 Task Force

- Memorist

Korean dramas =
Criminals working with an unconventional detective: Bad Guys [2014]
Criminals working with a cop: Player [2018]

  • W - ML runs a TV show that investigates cold cases. At various points he works with the cops, is framed for murder, is forced to lie to the authorities and is forced to go on the run.
  • I Hear Your Voice - FL is a defence attorney and the ML can read minds who helps the cops from time to time and wants to be a cop one day. They are both targeted by a killer and the ML enters into grey territory when trying to protect the FL. 
  • Hello Monster - The ML is an unconventional detective but is also connected to a serial killer and series of killings. His approach to dealing with the serial killer is unconventional. 
  • Misty - The FL's husband is a lawyer who takes on her defence when she is accused of murdering her ex. The detective on the case is frustrating to say the least. And it turns out that the husband was the killer all along.
  • The Girl Who Sees Scents - Killer works with the police.  
 AH :
Hello Monster

+1 great drama

Cruel City  - perfect drama in general, also I think perfect for you. It's about cops vs/with mafia, undercover cops in mafia, also mafia in legal system and realy complex, realistic situation where you don't know who are whos enemy or ally, twists and turns till the end, never boring or uninteresting, soo big turns and surprises. Amazing charismatic strong, smart and kind of mysterious anti hero ML, amazing bromance and romance (which is side story but soo emotional, mature and hot chemistry, it's one of my fav romance), every character is really great. Almost no one is black or white. Overall quite dark drama, fits name (another name of the drama - heartless city) but really one of best Kdrama, with high quality and production, no cliches or primitive details. also amazing OST

one of main theme is practically criminal working with police but can't say more because it's one of good surprises you will know after few episodes. Also SML detective and almost every detective there aren't traditional "good cops"