This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Trick 'r Treat
While still a horror film, most agree that the film is not a scare fest. However, almost everyone agrees that the ending to the school bus story is the most chilling moment in the film.
While we don't see anything of what's happening down below as Rhonda reaches the top of the cliff in the lift, the sounds of the kids screaming as they're torn apart - and then the sounds of whatever comes next - are extremely creepy.
Rhonda's face expression as she hears everyone be killed makes it worse, sort if hinting she's either undergone a Sanity Slippage or become flat out psychotic.