Antichrist (Lars von Trier, 2009)

 

But she says they don't stay in control as the film drifts into horror sequences. 

Wikipedia Plot of the film:

An unnamed couple has sex in their Seattle apartment while their toddler son, Nic, climbs up to the bedroom window and falls to his death. The mother collapses at the funeral, and spends the next month in the hospital crippled with atypical grief. The father, a therapist, is skeptical of the psychiatric care she is receiving and takes it upon himself to treat her personally with psychotherapy. She reveals that her second greatest fear is nature, prompting him to try exposure therapy. They hike to their isolated cabin in a woods called Eden, where she spent time with Nic the previous summer while writing a thesis criticizing gynocide. During the hike, he encounters a doe that shows no fear of him and has a stillborn fawn hanging halfway out of her.

During sessions of psychotherapy, the woman becomes increasingly grief-stricken and manic, often demanding forceful sex. The area becomes increasingly sinister to the man; acorns rapidly pelt the metal roof, he wakes up with a hand covered in swollen ticks, and finds a self-disemboweling red fox that tells him, "Chaos reigns!" In the dark attic the man finds the woman's thesis studies, which includes violent portraits of witch-hunts, and a scrapbook in which her writing becomes increasingly frantic and illegible. She reveals that while writing, she came to believe that all women are inherently evil. The man reprimands her for this, and in a frenzied moment, they have violent intercourse at the base of an ominous dead tree, where bodies are intertwined within the exposed roots. He suspects that Satan is her greatest hidden fear.

Upon viewing Nic's autopsy and photos she took of him while they stayed at Eden, the man becomes aware that she had been systematically putting Nic's shoes on the wrong feet, resulting in a foot deformity. While in the woodshed, she attacks him, accuses him of planning to leave her, mounts him, and then smashes a large block of wood onto his groin, causing him to lose consciousness. She then masturbates him, ejaculating blood. She drills a hole through his leg, bolting a heavy grindstone through the wound, and tosses the wrench she used under the cabin. The man awakens alone; unable to loosen the bolt, he hides by dragging himself into a deep foxhole at the base of the dead tree. Following the sound of a crow he has found buried alive in the hole, the woman locates, attacks, then partially buries him.

Night falls; now remorseful, the woman unburies the man but cannot remember where the wrench is. She helps him back to the cabin, where she tells him that only "when the Three Beggars arrive" he can die. She recounts Nic climbing up to the window, but she does not act, displaying her perceived essential evil. In the cabin, she cuts off her clitoris. The two are then visited by the crow (symbol of despair), the deer (symbol of grief), and the fox (symbol of pain), referred to as the Three Beggars. A hailstorm begins; earlier it was revealed that women accused of witchcraft had been known to have the power to summon hailstorms. When he finds the wrench under the cabin's floorboards, she attacks him with scissors, but he manages to unbolt the grindstone. Finally free, he viciously kills her, then burns her on a funeral pyre.

The man limps from the cabin, eating wild berries, as the Three Beggars look on, now translucent and glowing. Reaching the top of a hill, under a brilliant light he watches in awe as hundreds of women in antiquated clothes come towards him, their faces blurred.