This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Children of the Corn
The end of the short story. Burt and Vicky do not survive, there are no good kids, and the cult is not stopped. The fact that one of the cultists is pregnant with Malachi's child was somehow the most disturbing thing about these lunatics.
Made only slightly less horrific by the fact that in the short story, Burt and Vicky are complete assholes. Not to mention complete idiots.
The lack of exposition of exactly what happened in Gatlin in the original story is actually pretty terrifying on its own. The evidence Burt finds and pieces together paints a pretty horrifying picture on its own, but you dont see any of it happen unlike the 1984 adaptation, and the time skip between the massacre and the time of the story is also MUCH longer. The cult has been doing this for 12 years by the time Burt and Vicky finds them, and NO ONE has noticed it before. No one who lived to tell the tale anyway.
The sheer isolation of Gatlin is utterly soul crushing, imagine being trapped in a place like that, lost in a sea of vegetation, you might as well be the only town in the world.
The fate of Gatlin's original priest and the police chief in both versions.