“Based on true events” is an overused trope in recent horror films, with the term being used very, very loosely. But there’s no denying that for some of them, the reality is surprisingly scarier than the fiction.

The Real Killer That Inspired Psycho, Silence of the Lambs, and More
If you were to ask me my favorite horror films of all time, it would be a tricky question. But Silence of the Lambs and Psycho are at the very top of the list. Coincidentally, my two favorites have a common link: Norman Bates (from Psycho) and Buffalo Bill (from Silence of the Lambs) were both based on the same person.
That person is Ed Gein.
Gein was an infamous killer who, much like his fictional counterparts, had a collection of human organs. He made clothing and other accessories out of real body parts.

Robert the Doll is No Child’s Play
Chucky, the doll in Child’s Play (and Bride of Chucky, Curse of Chucky, a new TV series coming soon, and way too many other unnecessary remakes) was based on a real story.
Robert the Doll is now kept locked behind glass, on display in Key West’s Fort East Martello Museum. Visitors of the museum that disrespect him are said to get cursed by the doll’s evil wrath… a curse that has been around since 1903, when he was originally given to a young boy as a gift and wrecked havoc on the boy’s life.
Disrespect the Chucky remakes all you want. Just don’t insult Robert.

The Strangers: Because They Were Home
Although The Strangers was only loosely based on two events, its dialogue of “because you were home” speaks to the true events in a chilling way.
The two events? A series of break-ins in the director’s neighborhood that scarred him as a child… and the Manson Murders. Though The Strangers doesn’t have the cathartic ending as Once Upon a Time in Hollywood, it offers a creepier (and Brat Pitt-less) alternative to a Manson Murders family movie night.