This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Diablo II
Tristram, Holy crap! This village's people thought that the terror was over only for The Legions of Hell to come pouring out of the fallen Zakarum cathedral and raze the place. They've set up shop in the burning remains of the town, turning the blacksmith Griswold into a zombie, killing Wirt, and imprisoning and torturing Deckard Cain.
After the events of the first game, we see The Warrior who was then possessed by Diablo in a tavern with lots and lots of people. These people were drinking heavily until these people did some bad thing to The Warrior and that prompts him to unleash the Legions of Hell on that tavern and thus killing every single man except for Marius.
Going to the Rogue Monastery and facing a tonload of succubi is just plain wrong and horrible. Even worse if you face the Maiden of Anguish herself. Heaven have mercy!
Those aren't succubi. They're what happens to Rogues who get corrupted by Andariel, including Blood Raven, the original Rogue from the first Diablo. And the Rogues that didn't fall to her corruption? You can see their bloody and often naked corpses on stakes and various implements of torture scattered all about the place. Try not to think too hard about what these poor women went through at the hands of the demons before they died.
Completing the original three heroes from the original game is the Sorcerer, who after defeating Diablo, slowly lost his sanity and snuck into the Arcane Sanctuary. Here, he was corrupted by demons and possessed by the spirit of Horazon. He becomes the Summoner in Diablo 2.
How long do you have to walk through a desert if your damn camel dies of exhaustion? And what the hell was keeping Marius and Diablo from dying of thirst or exhaustion?
Tal Rasha. Sacrificing himself just to help the Horadrim and Tyrael seal Baal inside a tomb for good. Imagine fighting an extremely powerful demon inside of you just reeks off fear.
And then we go to the Cathedral of Light, the most holy place of the Zakarum faith, now known as the Durance of Hate as a result of Mephisto's evil twisting the place inside and out. You go all the way into a place full of demonically possessed people (and demons as well), up to and including all of the high priesthood of the Zakarum. Of whom Lazarus (one of the main villains of the original game and the one who released Diablo) was once a part. It truly hammers home that no place, and no one, is safe from the corruption of Hell.