Equality Before the Violence(2019)

Original title: 쎈놈

Dong-ho is ranked number 1 in "Arena," an illegal gambling league for teens, but he steps down to prepare for college. However, the members of "Arena" don't want to lose their biggest money-maker, so they place a debt on his brother Dong-min. Dong-min literally fights against his debt, but when he gets hurt, Dong-ho decides to fight back.