Where the killer decides, after a life and death struggle, to let the victim live anyway. It is important to note, however, that this doesn't serve to tell the audience what a naive, trusting fool the character is, rather it proves that the character has a moral conscience, and won't descend to their opponent's level. However, in an unexpected twist, the beaten victim mounts one last cowardly attack, giving our hero justification in ending their life. This shows the audience that the character not only has a heart, but they are strong enough to slay evil-doers if necessary. Things rarely get more exciting than this in a film, so if you are lucky enough to see it you should thank the Hollywood writers for having the courage to reuse it.