i think the most frightening horror movie, to me, is
The Others in 2001/2

The film is set on Jersey, one of the Channel Islands, in 1945, just after the end of the Nazi occupation in World War II. Grace Stewart, the wife of Charles Stewart (a soldier away at war, missing and presumed dead), fears for the safety of Anne and Nicholas, her children, who suffer from extreme photosensitivity, which means that if they are exposed to direct sunlight for too long, they could die. As the movie continues, the isolated house appears to be occupied by unseen (and possibly supernatural) "intruders".
Grace and her children obey a series of complex rules designed to prevent them from inadvertent exposure to sunlight. The new arrival of three servants at the house (an aging nanny, an elderly gardener, and a young mute girl) coincides with a number of odd events, and Grace begins to fear that they are not alone.
Anne draws pictures of four people -- a man and a woman, a boy called Victor and a scary old woman -- who she says she has seen in the house. A piano plays when no one is in the locked room.
Grace is strict, and a Catholic who follows the Bible closely. She tries hunting down the "intruders" with a shotgun but cannot find them. She scolds her daughter for nonsense about ghosts until she hears them herself. Eventually convincing herself that something unholy is in the house, she runs out in the fog to get the local priest to bless the house.
Out in the forest, Grace loses herself in the heavy fog, but miraculously discovers Charles, wandering on his way home, and brings him back to the house. However, he is distant, lonely, and stunned when Anne makes allegations about things her mother did to her. After spending one night with Grace, Charles disappears again.
Meanwhile, the servants - led by the aging Bertha Mills - are clearly up to something of their own. The gardener buries three gravestones under autumn leaves, and Mrs. Mills listens faithfully to Anne's allegations against her mother.
After Charles leaves, and Anne continues to see things - including "Victor"'s whole family, and a scary old woman, Grace breaks down to Mrs. Mills. Mrs. Mills claims that "sometimes the world of the dead gets mixed up with the world of the living". The two women also find and examine a 'book of the dead', which shows photographs taken in the 19th century of recently deceased corpses.
One morning, Grace wakes to the children's screams: all of the curtains in the house have been removed, and are missing. When the servants refuse to help look for them, Grace realizes that they are somehow involved. Hiding the children from the light, she banishes the servants from the house.
That night, Anne and Nicholas sneak out of the house and find the hidden graves. At the same time, Grace goes to the servants' quarters and finds a photograph from the book of the dead. As she turns the pages, she's horrified to find a picture of the three servants. Meanwhile, the children discover that the graves belonged to the servants. The servants, or rather ghosts of the servants, appear and give chase to the children, who make it back into the house just as Grace emerges to hold off the servants with a shotgun. The children run upstairs where they hide, but are found by the strange old woman.
Downstairs, the servants continue talking to Grace, telling her that they have to learn to live together. She begins to understand what they mean.
Upstairs, Anne and Nicholas discover the old woman is acting as a medium in a séance with Victor's parents. Judging from the clothes of Victor's parents, it seems that the actual time period is some time during the early 1950's. It is then that they learn the awful truth: the old woman is not the one who is a ghost; the ghosts are Anne, Nicholas and their mother. Grace loses her temper and supernaturally attacks the visitors. This sequence is quickly intercut with scenes from both Grace's viewpoint and the family's.
The truth is finally clear to Grace and the audience: She breaks down with the children and remembers what happened just before the arrival of their new servants; yearning for the company of her missing husband and increasingly frustrated by her children, she smothered them both with a pillow and then - realizing what she had done - shot herself. When she awoke, she assumed that God had granted her family a miracle.
Grace and the children presume that Charles is also dead. Although, Charles is aware of this which can be noted by his attitude shown in the film.
Mrs. Mills appears and informs Grace that they will learn to get along, and sometimes they won't even notice the living people who inhabit their house.
Outside, Victor's family - less than happy with their haunted house - pack up and move out. From the window, Grace and her children watch as they drive away. Grace ends the film with the line that "no one can make us leave this house."