Kuchisake-Onna

Kuchisake-Onna is the legend of a Japanese woman, mutilated by her jealous samurai husband who murdered her for infidelity, scarring her horribly and leaving her repulsive.
Her jealous Ghost still haunts places in Japan, usually on foggy nights. She wears a surgical mask, and she will approach people and ask shyly: “Anata wa watashi ga utsukushii toomoimasu ka?” (Do you think I'm beautiful?) The person usually responds, "Yes".

She then pulls down her mask to reveal an ear to ear grin, cut by her jealous husband to mark her for her life. “Even like this?” she will persist. If you answer no, she will reveal a pair of scissors and cut the same gruesome smile into your own face. If you answer yes, she will disappear, and the second you go home she will reappear at your door and finish the job.

There are several ways to prevent this terrible fate. One, to confuse Kuchisake-Onna by saying: You are average. Two, present her with hard amber candy, which she'll take much delight in and let you go. Three, say ‘Pomade’ six times, she will then flee. Four, ask her if you are beautiful, which will confuse her hopefully long enough to escape. Be wary, she is said to be incredibly fast and will be unlikely to stop.

She has been seen from the 1970s til the early 2000s, often seen lurking near children whose innocent answer of yes when asked if she is ugly, will lead to their deaths.

Credit to:
Creepypasta.wiki