3. Toby Kills Julie & Dennis (Paranormal Activity 3)
PA3 ends with the demon (now known as Toby) throwing Julie's limp body down the stairs at Dennis. As he tries to crawl away from all the carnage moments later, Toby, as watched by Julie's mother Lois, bends Dennis' back backwards, killing him instantly. It's a damn brutal effect and arguably the grimmest death in the franchise, all the more disturbing because Lois just watches the whole thing without a flicker of emotion, before heading off with Katie and Kristi.