Dr. Romero

Dr. George Romero is the true main antagonist of the 2010 Half-Life mod Nightmare House 2, serving as the player's guide for a majority of the game until he reveals he is a hostile sociopath.

Background
Not much is known is known about Romero's early life, but what is known is that he was happily married with Emily as a scientist, specializing in engineering, resurrecting the undead, and brainwashing. In one of his experiments, he used Emily as a test subject, but accidentally killed her. While he did desperately attempt to revive her, he revived her spirit instead and retreated to the mental institute Never Lose Hope Hospital where he secretly lived in it in the facility's shadow for months. During this, George constructed a large machine called The Core that infected people's mind and forced them to absorb hallucinations so realistic that it can actually harm/kill them. He also used his evil creation to ward off Emily's vengeful spirit.

Nightmare House 2
Becoming insane during his stay, George violently killed a majority of the hospital's residents after hearing that an individual (named The Patient) crashed his truck outside of the institute. The Patient was one of the only survivors of the mass murder and had his mind protected by Emily so The Core wouldn't infect his mind, which was already infected with insanity and hysteria due to the traumatizing events of Nightmare House 1. Romero then secretly attempted to kill the wandering Patient with the axe, but soon befriended him and became the Patient's guide. At the very end of the game, however, Romero reveals that he is behind Emily's death and the events appearing the games. He then attempts to murder The Patient with the Core, but is murdered himself by Emily's now restful spirit.