Perhaps 'I woke up to a cold breath on my neck. Looking in the mirror, I saw a figure that wasn't mine.' This is the kind of two - sentence horror story Naomi King might write. It gives a quick sense of dread. The first sentence sets the eerie scene, and the second one delivers a terrifying twist.
The brevity. In just two sentences, Naomi King can create a sense of unease. For example, 'I saw a shadow move. It had no body.' It gets right to the point and leaves the reader to fill in the blanks with their own worst fears.
Another really scary one could be 'My phone rang at 3 am. The caller ID said it was me.' It plays on the idea of the self being something other or unknown, and calls at that time are always spooky.
I think 'The clock stopped at midnight. Then I heard footsteps.' is quite scary. It gives this feeling of something ominous starting right at a spooky time.
Some two - sentence horror stories are truly spine - chilling. For example, 'I woke up to a noise in the kitchen. When I got there, all the knives were floating.' The simplicity of the setting and the unexpected, supernatural element make it effective. Another one could be 'She heard a baby crying in the attic. She doesn't have a baby.' It plays on our primal fears of the unknown and the unexpected in a very short space, creating a sense of unease and horror.