Very minor violence, mostly slapstick.
The protagonist slaps another man in the face. He also pushes the same man to the floor.
One of the characters is an ex-boxer. There are a few cutscenes which show him fighting in the ring, with rather graphic punching. He also punches one of the customers. No blood is shown.
There are a few scenes where the protagonist regurgitates violently into a lavatory pan. Non-explicit.
Two men get into a minor scuffle, though this is intended to be comic.
It is implied that Seon-Woo is being domestically abused, though this is never confirmed. His ex-lover is seen grabbing him forcefully on occasions and in one particularly distressing scene, he grabs his arm and bends it back; bones are heard cracking while Seon cries in pain.
Two characters are often seen cat-fighting, though this is mostly comedic.
In a flashback scene, it is implied a woman is stabbed in the throat in front of a young boy. Blood is seen spraying onto his face.
In another flashback, a boy stabs a man in the leg with a knife. The man pulls the knife from his leg with a small amount of blood spray.
At the movie's climax, the protagonist is seen strangling the suspected child abducter. The man's face is bloody and beaten. Probably the most gruesome part of the film, but still rather brief.