We went back and forth on whether we wanted to include “The Mist” in our countdown of the best horror movies of the last 15 years. But it wasn’t because we didn’t think it was scary. Precisely the opposite. “The Mist” offers one of the most unsettling portraits of human behavior that we’ve ever seen in a horror film. And it’s not because the characters are essentially bad people … they aren’t. They are normal, everyday folks who are driven to their limits by circumstances beyond their control. Sure the circumstance in this case happens to be spider-y monsters and a mysterious fog, but the social commentary remains the same. The anguish felt by main character David Drayton (played by Thomas Jane) at the film’s dramatic and traumatic conclusion is so palatable viewers nearly choke on it.