Nitro+/Nightmare Fuel

Nitroplus is one of the Darkest Visual Novel companies in existence to this day. Their works would generate nightmares even without the help of Gen Urobuchi. However, with Urobutcher in the Driver Seat, their works gives Hideaki Anno, 07th Expansion, and Junji Ito a run of their money of THIS.

Phantom of Inferno
The company's first Visual Novel while simplistic in comparison to the later ones, sums up the first impression of their works very well: DARK. The story follows the life of a young man who sees something he shouldn't have seen, is captured and Brainwashed by a shadowy organization called Inferno and then is given the choice "join or die". He is trained as an assassin by a soft-spoken girl called Ein. Ein is Inferno's top assassin, code-named "Phantom" and controlled by the sinister Scythe Master, who also brainwashed the man. The man is given the name Zwei and begins his work at Inferno. It Gets Worse from there.

Saya no Uta
THIS is what you get if H.P. Lovecraft worked in Visual Novels. Fuminori's 24/7 Dark World Gorn senses, cannibalism, Body Horror , Adult Fear , The End of the World as We Know It , you may share 's sediments to Go Mad From the Revelation. The soundtrack itself is very unsettling to say the least. Here is a small step-by-step summary of ALL ITS HORRORS:
 * First, the Dark World Gorn senses, yeah it is Exactly What It Says on the Tin. The first location you are at is in a local restaurant but due to the senses it looks like something from a terrible nightmare that Fuminori can never wake up from and he has very difficulty understanding his original friends, eating normal food, or even looking at them. The sad part about it, . A normal person would have committed suicide a long time ago, and then he meets Saya.
 * Saya, just Saya,
 * Cannibalism, this was coming due to Fuminori's warped senses but the way it is described is horrifying on Fuminori's POV and who the person that he is eating from, . Soon after this.
 * Body Horror. The most prominent being
 * Adult Fear. Picture this scenario: Yeah,  had it rough.
 * Dear God, Seeing   was too much.
 * Now we start to get to the endings, no matter which ending you got someone WILL have a Fate Worse Than Death . Those people are:
 * Fuminori This ending is achieved.
 * Dr. Tanbo . This ending is achieved.
 * And finally, Kouji . In this ending,.

Chaos;Head and Steins;Gate

 * This is what you get if Nitroplus creates a Mystery fiction. All the New Gen murders in the game have mysterious elements, particularly the second, in which the dead man . It is eventually shown, in flashback, how this happened. And this is just the beginning.
 * There is also Takumi's red delusions, as the green delusions are lighthearted, funny, and erotic, the red ones are the polar opposite, darker, tragic, and Nightmare Fuel.
 * Time Travel seems awesome doesn't it? Not if someone else decides to try to hunt you down and that every action caused in that time period results in the Butterfly of Doom.

Nitro+ CHIRAL (Nitroplus Boys Love works)

 * Togainu no Chi: Keisuke's route involves Akira  and one Bad Ending has  . Also YMMV but Arbitro's modification to his pets which include removing their eyeballs and windpipe. Not to mention completely breaking the victim's mind so that they act like dogs or worst. This becomes Fridge Horror in Arbitro's Bad End since.
 * Another one of the bad endings on Keisuke's route is  And you want to know how to make the other bad ending worse? Do you?
 * On one of the Executioner endings, Kiriwar
 * One of Shiki's bad endings;  He scares Akira so much that he's practically sobbing. But wait! It gets better!
 * After entering Toshima, Akira comes across two guys having sex. One of them Is. Not. Moving.
 * To add on the above, one of the rules of the Igura is that the winner not only takes the loser's tags but they can do whatever they want to the loser. And, as Keisuke points out, there aren't any females in Toshima...
 * Lamento Beyond The Void: Shibiku. Enough said.
 * Sweet Pool only had Urobuchi Gen as an advisor but is still chock full of Squick, Body Horror and Mind Screw. The basic premise has Youji, the main character as the host of the female form of a parasite that makes him . Like Saya no Uta, the endings are Bittersweet at best but  ending involves him.

Other (other Nitroplus works and collaborations with other companies)
Fate/Zero (collaboration with Type Moon)

See respective page.

Puella Magi Madoka Magica (collaboration with Studio Shaft)

See respective page.