The Slit-Mouthed Woman (2007)

The film is based on a Japanese legend in which a samurai's wife was caught cheating on him, and he slit her mouth open. The same woman roams foggy streets, with a surgical mask on, and asks people she encounters, "Am I beautiful?". If they say, "Yes" she removes her mask and says, "Even like this?", and then slits their mouth. If they say "No" she cuts them in half. If they say "Average", she will allow them to escape.