Strangers from Hell (2019): Man moves to Seoul and gets beyond horrible neighbours. Psychological thriller that's phantastic. It's on Netflix but it's leaving in the middle of May, so I would watch it soon.
The King of Pigs (2022): A serial murder case wrapped around the effects of school violence. The best drama of the year so far IMO. It has a lot of complex and nuanced character writing, amazing acting, and the technical aspects (cinametography, editing...) are great as well.
Through the Darkness (2022): The Korean variant of Mindhunter. Based on the book of the first korean profiler and real life cases he confronted. Great acting. The interviews with the criminals are utter highlights.
Stranger (2017): Great story, and amazing ending. It leaves you thinking about issues of morals, choices and justice. Great platonic male-female duo.
Beyond Evil (2021) Perfect. The story, the characters, the acting, the pacing, the cinamatography and so on. It's one of my favourite crime shows overall.
Signal (2016): Crime story meets time travel. Two cops communicate through a walkie-talkie and time to solve crimes.
The Fiery Priest (2019): A more comedic take, if that's okay. A priest with loooots of anger issues vs. corruption and criminals. IT's a fun crime story and the character interactions are hilarious. The character development of them and their relationships is A+