Kim Hyoung-jun's 2010 debut feature No Mercy is the sort of twisted revenge thriller that many casual fans associate with post-2000s Korean cinema. It has drawn many comparisons with Park Chan-wook's Oldboy, mostly due to the concluding twist, which fairly shamelessly cribs from that earlier film. However, the more pertinent comparison would be to another Korean film, Won Sin-yeon's 2007 film Seven Days, in which Yunjin Kim (Lost) plays a lawyer who is compelled to seriously compromise her ethics and help free a convicted murderer to release her daughter from a kidnapper.
A very similar situation sets up No Mercy. Kang Min-ho (Seol Kyeong-gu), one of Korea's top medical examiners, is ready to retire to reconnect with his daughter, who is returning to Korea after studying abroad. Before his planned retirement, he investigates one last case of a young woman who has been found murdered and dismembered by a river. With the help of Min Seo-young (Han Hye-jin), a female rookie detective, and a former student of Kang's, the investigation leads to Lee Seong-ho (Ryoo Seung-bum), an environmental activist protesting a river development project. Seong-ho, after being interrogated by Detective Min, soon confesses to the crime, but this is far from the end of the story. Kang, while waiting for his daughter to arrive at the airport, is informed by phone (and pictures given him by a stranger) that his daughter has been abducted, and to free her, he must get Seong-ho off the hook for his murder. After some intense interrogation-room confrontations with Seong-ho, Kang scrambles to taint evidence to frustrate the police's efforts to tie Seong-ho to his crime. Kang's efforts to stay ahead of the police while tracking down his daughter's abductors eventually reveals a connection between Kang and Seong-ho. Without giving too much away, the film's final scenes reveal that all of this is an elaborate plot on the part of Seong-ho to avenge a wrong done to him that Kang had a hand in.
Writer-director Kim Hyoung-jun supplies the slick, noirish visual surfaces we have come to expect from Korean thrillers of this sort. The swift, headlong pace of the film helps to cover the fact that much of the details are rather absurd, not the least of which that Kang's role seems to eclipse that of the police in this investigation, to the point of him being allowed to interrogate and beat suspects just like the police. Also, originality is not exactly this production's strong suit, as the Oldboy-style revenge plot and its accompanying wicked twist indicates. Despite all this, No Mercy manages to be a riveting, and effectively diverting thriller, largely due to the scenes in which the great actors Seol Kyeong-gu and Ryoo Seung-bum face off, which provide an electric intensity to help to lift it above the banalities that often plague many films of this genre.
The DVD from CJ Entertainment America includes fairly standard extras, such as behind the scenes footage, trailers, and interviews with Seol Kyeong-gu, Ryoo Seung-bum, and Han Hye-jin. There are a few interesting details in these featurettes, such as a brief profile of an actual pathologist who was a consultant on the film. One key scene of No Mercy involves Kang cutting open the murdered woman's body for examination, the gruesome details of which are lingered upon. The pathologist points out that, contrary to the way this is usually depicted in film and television, when a body is cut open for autopsy, there is actually very little blood; only a living person bleeds copiously when cut open. Despite his objections, and insistence on verisimilitude in this matter, the director insisted on blood for the dramatic effect. Other interesting on-set tidbits include Seol and Ryoo's contrasting acting styles: Seol's workmanlike, "leave it on the stage" approach, as opposed to Ryoo's Method techniques of always remaining in character.