City of Fathers (2009)

Kang-soo is a third-rate street thug in Busan; he's an alcoholic and gambling addict who's always on the run from loan sharks. But when his rebellious teenage son Jong-chul is diagnosed with kidney cancer, he tries to be a real parent for the first time and seeks out Jong-chul's biological father, Tae-suk, a pimp. Tae-suk, however, refuses to help.