I, the Executioner — Ending Explained

The Big Reveal: Park Sun-woo is Haechi
Midway through the film, the narrative unveils that rookie officer Park Sun-woo is not tracking Haechi—he is Haechi. Having infiltrated Seo Do-cheol’s unit under the guise of an eager recruit, Sun-woo uses police intelligence to stay ahead of the investigation while orchestrating public executions of unpunished criminals.

The Frame-Up of Min Kang-hoon
To divert suspicion when the Major Crimes Unit closes in, Sun-woo abducts Min Kang-hoon (Ahn Bo-hyun), a vulnerable ex-convict. Sun-woo drugs Min, dresses him in Haechi’s signature attire, and stages an elaborate rooftop confrontation to fool Do-cheol and the public into believing the serial killer has been identified and neutralized.

Climax and Showdown
Recognizing inconsistencies in the frame-up, Do-cheol uncovers Sun-woo's true identity. In retaliation, Sun-woo kidnaps both an antagonistic cyber-wrecker streamer and targets Do-cheol’s family, forcing Do-cheol into a vicious, bone-crushing showdown in an abandoned tunnel and drainage facility. Sun-woo taunts Do-cheol, trying to push the veteran detective to cross the line and execute him on a live camera stream, proving that Do-cheol is no different from Haechi.

The Resolution and Post-Credits
Do-cheol manages to incapacitate Sun-woo. When Sun-woo suffers a near-fatal injury and stops breathing, Do-cheol chooses not to let him die. Instead, Do-cheol desperately performs CPR, forcing life back into Sun-woo's lungs so that he can stand trial under the law. Sun-woo is placed under arrest, reaffirming the dignity of legal process over murder. A mid-credits sequence hints at ongoing institutional friction and the future continuation of the franchise, setting the stage for Veteran 3.

Park Sun-woo: Ideologue or Thrill-Seeking Sociopath? One prominent debate is whether Sun-woo genuinely believes his twisted moral dogma or if the "Haechi" vigilante persona is simply an excuse to inflict violence legally and illegally. His clinical lack of empathy suggests that moral justice was merely the stage for his psychopathy.

The Complicity of the Crowd: Another reading interprets the film as an indictment of the general public rather than just the killer. By cheering on Haechi's brutal livestreamed executions, society itself functions as the primary villain, creating the monster it claims to need.

The Ending Resuscitation: Do-cheol’s decision to perform CPR on Sun-woo can be viewed either as a victory of democratic human rights or as an agonizing, self-defeating burden of the legal system, which forces police to save predators who would not hesitate to kill them.