The Good Bad Mother — Ending Explained

The central mystery reveals that Kang-ho’s villainous behavior was an elaborate covert operation. As a young prosecutor, Kang-ho discovered that Song Woo-byeok and former prosecutor Oh Tae-soo conspired to murder his father Hae-sik decades earlier and staged it as a suicide to seize agricultural land. To bring down these powerful figures, Kang-ho adopted a ruthless persona, broke up with his pregnant girlfriend Mi-joo, and legally disowned his mother Young-soon to earn Woobyeok's absolute trust and shield his family from retaliation.

Before Kang-ho could enact his plan, Oh Tae-soo orchestrated the car crash to assassinate him, resulting in severe brain trauma and mental regression to age seven. During Kang-ho's rehabilitation in Jou-ri Village, Young-soon discovers his hidden SD card behind their family portrait and realizes her son never hated her. Armed with recovered memories and evidence, Kang-ho stands in court as prosecutor, successfully convicting both Song Woo-byeok and Oh Tae-soo. Having witnessed justice served and her son happy and reunited with Mi-joo and his twin children, Young-soon passes away quietly in her home.

One dominant critical reading explores the subjectivity of the title: to a child, being subjected to forced starvation and isolation is unambiguously abusive and "bad," but to a traumatized, uneducated mother who knows the legal system can crush powerless farmers, her actions were seen as the only viable path to survival. Another interpretation posits that Kang-ho’s mental regression was not merely physical brain trauma, but a psychosomatic escape mechanism allowing him to shed the suffocating burden of his revenge plot and reclaim the lost childhood he had sacrificed.