I don't know the least interesting horror movies I've seen but what I always know that if it's not horrific, it won't be so easy for me to complete. One of such movie I couldn't complete because of not too interesting is The Black Phone, I didn't understand what they meant in the movie.

The Turning feels disjointed especially with its vague ending that frustrates more than it frightens. The atmosphere was good but the story collapses under its own ambiguity.

For me, The Open House was a letdown. It started with promise, but the ending felt unsatisfying, and I finished it wishing it had done more.