Public Enemy (2002) on Netflix

Ruthless cop Chul-joong and a merciless killer in raincoat run into each other in a small alleyway and form a fatal bond. A free-for-all fight occurs by coincidence on a rainy street. A week later, the dead bodies of an old couple are discovered with multiple stab wounds. Chul-joong suddenly recalls the night he met the man in the raincoat. Chul-joong meets the old couple's son CHO Gyoo-hwan. He has an intuition that CHO is the murder but has no clue. In the meantime, another murder takes place in the same fashion. The showdown between a dirty cop and a killer unfolds, as things get more personal.