This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Phantasmagoria 2
Despite its excessive amounts of Narm, the game still delivers a few honestly scary moments. Ironically for a game/film with such slick-looking gore effects, the game is at its best when it does subtle atmospheric horror.
The blink-and-you'll-miss-it phrases like "USURPER" and "EAT THEIR EYES" that keep popping up in your email are especially effective. At least until you end up fishing through the email system long enough to get used to it.
One example of this is in the asylum. One patient is an old woman who keeps calling Curtis a freak and claims that she saw him and knows what he did. She actually bites her wrists, causing some bleeding, and holds her hands up high, saying a prayer to God. Curtis shows an appropriate demonstration of Squick towards that. That alone was nasty, but here comes another interesting detail. There are indications that the Hecatomb may have been acting through her (and maybe some other people there), as part of an attempt to drive Curtis insane. That scene certainly contained this trope.
The Hecatomb explicitly states that it survives by eating people- live people- who are apparently supplied by Paul Warner. First of all, where and how does Warner get these victims?
Keep in mind; the Hecatomb has been alive for twenty years by the time the game begins.
Even worse, if The Stinger is anything to judge by, the cannibalization process is slow, and you're completely conscious and aware of everything as it happens.
Incidentally, the Stinger shows Paul Warner's severed head suspended in Dimension X, and he gasps, implying that he's still alive. (for now...)
Warner gets them from the Greenwood insane asylum. Or he used to. During one flashback he's seen ordering Jonas Craig to go fetch more inmates from Dr. Marek when the guy they try putting through the portal dies of fright.
It's implied that it's not only the Hecatomb who cannibalizes live humans- the basic life forms of Dimension X do too. Imagine it... an entire dimension full of beings who use live humans as a food source.
The Hecatomb's backstory is pretty horrifying to think about as well. A young child thrown into an alternate dimension with no means of return. The only beings around aren't even capable of communication with him. When Curtis encounters the true form of the Hecatomb he's a hideously mutated human incapable of moving or even breathing unaided with no interaction with any other beings. There's no hint of how long he's been this way, but it's implied to have been a very long time. He is only able to interact with the outside world via a projection of his will. The Hecatomb's situation is only a step above And I Must Scream and he's been in this state for many many years.