The Curse of Sadako's Phone Number
The film tells the creepy story of a woman named Sadako who gives curse to anyone who have seen her video. Watching her video will bring you to your own death, you will get the confirmation that you have the curse through Sadako as well. In the film, Sadako calls anyone who have seen the video right after they stopped watching the tape.
In all versions of the Ring cycle, she appears as a shadowy young woman dressed in white, whose face is concealed behind her long black hair. The first film explains that, as a young girl, she was thrown into a deep well and left to die. Her spirit survived, however, and put itself into a video tape that kills anyone who views it unless someone else watches it within seven days. If not, Sadako herself emerges from the television screen, and the viewer dies of fright - wikipedia
It is already a no-brainer that Sadako is one of the most scary and creepy horror film antagonists of all time. And it looks like that her legacy is not going to be forgotten anytime soon as another urban legend was said to be from her as well. The phone number from hell also known as SADAKO's phone number.