Here are some: 'Alone in the dark.' It gives a sense of isolation and the unknown in the darkness which is quite terrifying. Another one could be 'Footsteps, no one there.' Just the idea of hearing footsteps but seeing no one is really spooky. And 'Lost in the forest' also works. Being lost in a vast and often unpredictable forest is a nightmare scenario.
Well, 'Dark Stare' can be a very chilling '2 word horror story'. 'Cold Hand' gives a sense of unease too. Also, 'Hidden Face' is quite spooky.
Here are some: 'Bedroom door creaks.', 'Footsteps in attic.', 'Eyes in the dark.'
One: In the mirror, a face not mine. I blink. It doesn't. I run. It follows.
How about 'Knock, no one there.' You hear a knock at the door, but when you open it, there's nobody. It leaves you with a sense of unease and the feeling that something is playing tricks on you.
Here are some: 'Alone in the dark.' It creates an immediate sense of isolation and the unknown that lurks in the darkness.
Here are some: 'Eyes in dark.', 'Footsteps behind me.', 'Face at window.'