The Horror Challenge,
A movie that kills of countless main characters.
Wow, there are tons of movies coming through my mind, in almost every horror movie everybody dies except for one of maybe two people. The Mist is the first that came up in my mind though, I won't give out any spoilers but if you've seen it, you'll know what I mean.
Others movies that came to my mind where for example: Cloverfield, The Blair Witch Project, Cabin in the Woods, Saw 2 and so many more.