Demonophobia

Demonophobia is a 2D survival horror game by an anonymous Korean developer under the user name of "237". It has been uploaded to a file-sharing resource in mid-2008 and after one month it had over 10,000 downloads. The game became infamous for being extremely gory and disgusting and gained a somewhat cult status. It follows the "Hentai Ryona game" scheme; when you lose, the protagonist (in this case, Sakuri Kunikai) dies by extremely gory and sadistic deaths. Also, the game features trial and error (or more like "trial and death") gameplay which means that many deaths are unavoidable.

In October, 2008 the developer published a demo of Xenophobia, a Demonophobia sequel (though it has nothing to do with Demonophobia in terms of story), which promised to be a massive improvement over Demonophobia in terms of quality. On December, 2009 a second demo has been published, but there were no more news from the creator after this.

In April 2012, the game got a spiritual successor named Splatter School. There is also another spiritual successor under development named PrisonKage.

Plot
Sakuri Kunikai, a 14-year-old Japanese schoolgirl, lived in a modern world and never believed in supernatural things. One day she found a book about black magic and decided to perform a demon summoning ritual, just out of interest. The ritual worked, but as an result, Sakuri herself got trapped in a horrible world of demons. The girl left absolutely alone, in a disgusting world full of horrible creatures, she didn't know what to do and almost lost hope... but suddenly she saw a phantom named Ritz. Ritz told her that the place she needs is in the very center of the demonic labyrinth, and Sakuri went there, determined to get back to home...

Why It Sucks

 * 1) Getting the cat out of the bag, this game has  some of the sickest content that you will probably ever come across in your life.  The very premise of this game is to watch Sakuri, a 14-year-old girl, suffering and dying in every possible way. The death scenes are unskippable, even after the player has watched the same death sequence dozens of times, and this will happen for most people considering the fake difficulty.
 * 2) * To add insult to injury (although not a bad point for some people), the ending is pretty depressing.
 * 3) Bad controls. The worst part is the inventory control; you can even be hurt heavily or killed by a boss during switching between items.
 * 4) The game can also be considered animated child pornography, especially at the fifth boss fight and the last level, where Sakuri is naked for no apparent reason.
 * 5) The graphics look like they were made in MS Paint. The animations are also poor.
 * 6) The game features health regeneration, which makes life much easier, but it's hard to notice it. And even if you know about it, standing still long enough to recover all health is not a good mechanic.
 * 7) The health indicator (Sakuri's portrait) disappears during the boss fights. Because of this, you cannot know whether Sakuri takes damage.
 * 8) The last two bosses bosses are infuriatingly difficult, even more so than the rest of this game. The final boss remains hard even if you freeze the HP via CheatEngine, because he has instant-killing attacks that ignore HP entirely.
 * 9) The game lacks any sound effects and music, which is both a good thing and a bad thing. Sure, you don't have to listen to Sakuri screaming in agony or flesh and bone being torn asunder (among other things), but at the same time, it can detract from the experience for those who actually enjoy this game. And yes, such people actually exist. God help us all.

Redeeming Qualities

 * 1) The game can be considered challenging.
 * 2) The story is not bad. Coupled with the story, this game is actually good at being a horror game if one doesn't care for the gruesome ending.
 * 3) * All the bosses have names in the source code, and most of them are named after Christian/Jewish mythological demons. Their roles on the game are also somewhat coherent with the demon they represent.
 * 4) * The game's setting is somewhat similar to Clock Tower: the First Fear and I Have No Mouth And I Must Scream, but this may have been just a coincidence. Also of note is that Clock Tower being notable for the well-drawn 2D corridors, multiple death scenes, and a defenseless young girl as the protagonist, the main difference being that Human Entertainment skimped out on the more gruesome bits of Jennifer's many deaths, while 237 had the balls to show you everything that happens to Sakuri.
 * 5) At least some effort was put into level design, puzzles and bosses: you actually have to use your brain.
 * 6) The game takes 8 MB of disk space when archived and 194 MB when unarchived, so you don't have to erase the game in order to spare disk space.
 * 7) The ending plays with video game tropes by explaining why you can restart the level after death. It also explains some things one might consider as bugs.
 * 8) As mentioned above, there's no sound or music. No screams of terror and death, no squelching, no demonic screeches... nothing. To some, this detracts from the experience. To others, however, it actually adds to it.