Nightmare Fuel / Extermination (2001)

• There is quite a bit of it here, from living water attacking you if you step in the puddles, Meat Moss growing everywhere and consuming everything in reach, to the Infected forms and the Eldritch Abomination that is the Big Bad of the game. Reading the description of Dennis' various infection levels can be pretty creepy as well as it describes exactly how painful the infection is on his body.
  • The Infection mechanic is this in general, given most protagonists in these games are The Immune. As soon as Dennis' infection reaches 100%, some sort of "core" or organ bursts out of his back (previous comments on his infection stated his back was hurting worse and worse the further his infection climbed), his max health is decreased by 40%, and he takes 5HP of damage every few seconds until he either gets to an MTS bed and cures himself (the meds that cure infection in the field no longer work) or dies from it, at which point his body mutates into a horrible monster as he can only gasp out in agony with his last breath. In addition, the music changes to "Infected!", which overwrites all music until Dennis is cured, and is a tense, scary theme that fully encapsulates the dire circumstances and the fear of dying and becoming the very monsters you're fighting against. To say the least, it is one of the scariest mechanics of the game, especially since so many enemies and hazards can easily infect Dennis.