Antichrist (2009)

After the tragic death of their child, a grieving couple retreat to a remote forest cabin in an attempt to heal, only for nature, sexuality, and madness to spiral into escalating terror. As grief transforms into sadism and psychological collapse, reality fractures into hallucinatory violence and cosmic dread. Antichrist is an uncompromising arthouse horror experience driven by extreme imagery, sexual psychosis, and existential despair.

Från IMDB:
A grieving couple retreat to their cabin in the woods, hoping to repair their broken hearts and troubled marriage, but nature takes its course and things go from bad to worse.