This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Jason Goes to Hell: The Final Friday
What happens to Jason's victims after he leaves their bodies, as Josh unfortunately finds out. As Jason leaves his body to possess someone else, Josh gruesomely starts rotting away, the highlight of this process being his jaw falling off.
For how little you see of him in the film, Jason's actual physical appearance is rather horrific. He's become so battered and beaten over the course of the franchise that his mask has been fused to his face, with scarred, bloated flesh growing around the edges.