The very idea of Uber Jason, in addition to being awesome, is somewhat terrifying. He's already proven himself to be all but invincible, even when his body is decomposing to the point that large portions of his skeleton are exposed to the elements. The idea of someone like that being given cybernetic upgrades is unnerving, to say the least.
Kay-Em's Slasher Smile after she upgrades to fight Jason has to count. When an android is having fun...
Jason dunking Adrienne in a sink filled with liquid nitrogen, pulling her out, and then slamming her face-first onto a counter. The counter wins.
Janessa's death. The vacuum of space pulls her entire body through a fist-sized hole currently covered by a grate. The camera cuts away, then cuts back to show all that's left is some scraps of bloody flesh clinging to the grate. It's all too easy to imagine what happened.
The dead, polluted Earth, now abandoned by humanity. Arguably the most upsetting part of the film.
