A Bittersweet Life (2005)

Gangland boss Kang suspects his girlfriend of being unfaithful and sends his trusted right-hand man Sun Woo, to sort out the problem. In an uncharacteristic moment of weakness, Sun Woo falls for Hee Su, taken in by her grace and humanity. When Sun Woo finally catches Hee Su with her lover, he finds himself unable to kill her and allows her to flee. This infuriates Kang who orders his thugs to savagely beat him and leave him for dead. However, they do not finish the job, and when Sun Woo eventually revives himself, he has nothing but vengeance on his mind.