I Am Trash (2016)

Same actors, same director, same gritty violence and sexuality. Both show sexual abuse in the South Korean military, as well.

Both films star Lee Sang Woo. Both show gritty homosexual interactions and military abuse of power.

Both star Lee Sang Woo. Both deal with perverted individuals and sexual abuse.

Father Is A Dog is the second instalment of Lee Sang-woo's thematic "bad family" trilogy, the first being Mother Is A Whore (2011), and the third being I Am Trash (2016). Both films have same director and feature the same actor. They both include themes of perverse sexuality, abuse, and homosexuality.

Both films depict some form of South Korean military abuse. I Am Trash has a much smaller segment of it.

These films have two totally different tones and themes, but they share the same depiction of sexual abuse in the South Korean military.

Both films show a soldier in the South Korean army who is harrassed and abused (mentally and sexually) by his superior.