The Most Disturbing Anime Ever Made

After being raped by an evil feudal lord and subsequently getting banished from her village, a peasant girl makes a pact with the Devil to gain magical powers and take her revenge.

A pop singer gives up her career to become an actress, but she slowly goes insane when she starts being stalked by an obsessed fan and what seems to be a ghost of her past.

Devils cannot take form without a living host. However, if the will of an individual is strong enough, they can overcome the demon and make its power their own, becoming a Devilman. Weak and unassuming, Akira Fudou has always had a bleeding heart. So when his childhood friend Ryou Asuka asks for his help in uncovering devils, Akira accepts without hesitation. However, to Akira's surprise, the place they go to is Sabbath: an immoral party of debauchery and degeneracy. Amidst bloodshed and death, demons possess the partiers, turning their bodies into grotesque monsters, and begin wreaking havoc. In a reckless attempt to save his best friend, Akira unwittingly merges with the devil Amon and becomes a Devilman, gaining the power to defeat the remaining demons. Though it grants him great power, this new partnership awakens an insatiable and primeval part of Akira. Having the body of a devil but the same crybaby heart, Akira works alongside Ryou, destroying those that harm humanity and his loved ones. [Written by MAL Rewrite]

Two teenagers take in a mutant girl who has lost her memories.

Peaceful schoolgirl by day, fearsome monster slayer by night, Saya Kisaragi is leading a split life. Equipped with a ceremonial sword given to her by her father for sacred tasks, she vanquishes every monster who dares threaten her quiet little village. But all too soon, Saya's reality and everything she believes to be true is tested, when she overhears the monsters speak of a broken covenant—something she knows nothing about. And then, unexpectedly, a strange dog appears; it asks her to whom she promised to protect the village, curious as to what would happen if she were to break that promise. Tormented by unexplainable visions and her world unraveling around her, we travel with Saya through her struggle to find a way to the truth in a village where nothing is as it seems. [Written by MAL Rewrite]

The relative coexistence of the human world, demon world and beast world is soon to be disrupted by The Overfiend, an immensely powerful demon who'll be reborn after 3000 years to remake the world to his own liking.

Kanto Hell Earthquake has demolished the metropolitan completely. After the earthquake, Slum King is kidnapping girls and sell them as sex slaves. Mari is wandering on the devastated field looking for her lover, Ken. But she is also kidnapped by them. While she is tortured and trained as a sex slave, Ken saves her. Ken has become the member of Slum King. The king offers condition to him; in return for releasing her, he has to kill Violence Jack. (Source: AniDB)

In the town of Kurouzu-cho, Kirie Goshima lives a fairly normal life with her family. As she walks to the train station one day to meet her boyfriend, Shuuichi Saito, she sees his father staring at a snail shell in an alley. Thinking nothing of it, she mentions the incident to Shuuichi, who says that his father has been acting weird lately. Shuuichi reveals his rising desire to leave the town with Kirie, saying that the town is infected with spirals. But his father's obsession with the shape soon proves deadly, beginning a chain of horrific and unexplainable events that causes the residents of Kurouzu-cho to spiral into madness. [Written by MAL Rewrite]

Guts, a man who will one day be known as the Black Swordsman, is a young traveling mercenary characterized by the large greatsword he carries. He accepts jobs that offer the most money, but he never stays with one group for long—until he encounters the Band of the Falcon. Ambushed after completing a job, Guts crushes many of its members in combat. Griffith, The Band of the Falcon's leader and founder, takes an interest in Guts and duels him. While the others are no match for Guts, Griffith defeats him in one blow. Incapacitated and taken into the Band of the Falcon's camp to recover, Guts wakes up two days later. He confronts Griffith, and the two duel yet again, only this time with a condition: Guts will join the Band of the Falcon if he loses. Due to his fresh injuries, Guts loses the fight and is inducted by Griffith. In three years' time, Guts has become one of the Band of the Falcon's commanders. On the battlefield, his combat prowess is second only to Griffith as he takes on large groups of enemies all on his own. With Guts' immense strength and Griffith's leadership, the Band of the Falcon dominate every battle they partake in. But something menacing lurks in the shadows, threatening to change Guts' life forever. [Written by MAL Rewrite]

A secret military project endangers Neo-Tokyo when it turns a teenage biker gang member into a rampaging psychic psychopath who can only be stopped by his best friend.

Concurrent theatrical ending of the TV series Neon Genesis Evangelion (1995).

While protecting a signatory to a peace treaty between their peoples, a male human and a female demon discover that their mutual attraction may be the key to unifying their worlds.

This is a horror story of the pure trembling love of a girl named Satou Matsuzaka.

The Abyss—a gaping chasm stretching down into the depths of the earth, filled with mysterious creatures and relics from a time long past. How did it come to be? What lies at the bottom? Countless brave individuals, known as Divers, have sought to solve these mysteries of the Abyss, fearlessly descending into its darkest realms. The best and bravest of the Divers, the White Whistles, are hailed as legends by those who remain on the surface. Riko, daughter of the missing White Whistle Lyza the Annihilator, aspires to become like her mother and explore the furthest reaches of the Abyss. However, just a novice Red Whistle herself, she is only permitted to roam its most upper layer. Even so, Riko has a chance encounter with a mysterious robot with the appearance of an ordinary young boy. She comes to name him Reg, and he has no recollection of the events preceding his discovery. Certain that the technology to create Reg must come from deep within the Abyss, the two decide to venture forth into the chasm to recover his memories and see the bottom of the great pit with their own eyes. However, they know not of the harsh reality that is the true existence of the Abyss. [Written by MAL Rewrite]

Lain Iwakura, an awkward and introverted fourteen-year-old, is one of the many girls from her school to receive a disturbing email from her classmate Chisa Yomoda—the very same Chisa who recently committed suicide. Lain has neither the desire nor the experience to handle even basic technology; yet, when the technophobe opens the email, it leads her straight into the Wired, a virtual world of communication networks similar to what we know as the internet. Lain's life is turned upside down as she begins to encounter cryptic mysteries one after another. Strange men called the Men in Black begin to appear wherever she goes, asking her questions and somehow knowing more about her than even she herself knows. With the boundaries between reality and cyberspace rapidly blurring, Lain is plunged into more surreal and bizarre events where identity, consciousness, and perception are concepts that take on new meanings. Written by Chiaki J. Konaka, whose other works include Texhnolyze, Serial Experiments Lain is a psychological avant-garde mystery series that follows Lain as she makes crucial choices that will affect both the real world and the Wired. In closing one world and opening another, only Lain will realize the significance of their presence. [Written by MAL Rewrite]

Two detectives try to uncover the identity of a mysterious, roller-blading boy who has been terrorizing Tokyo by assaulting seemingly random citizens with a golden baseball bat.

In the light of day and in the dead of night, mysterious horrors await in the darkest shadows of every corner. They are unexplainable, inescapable, and undefeatable. Be prepared, or you may become their next victim. Sit back in terror as traumatizing tales of unparalleled terror unfold. Tales, such as that of a cursed jade carving that opens holes all over its victims' bodies; deep nightmares that span decades; an attractive spirit at a misty crossroad that grants cursed advice; and a slug that grows inside a girl's mouth. Tread carefully, for the horrifying supernatural tales of the Itou Junji: Collection are not for the faint of heart. [Written by MAL Rewrite]

When Keyaru acquired his powers as a Hero who specialized in healing all injuries regardless of severity, it seemed that he would walk the path to a great future. But what awaited him instead was great agony; he was subjected to years of seemingly endless hellish torture and abuse. Keyaru's healing skills allowed him to secretly collect the memories and abilities of those he treated, gradually making him stronger than anyone else. But by the time he reached his full potential, it was far too late—he had already lost everything. Determined to put his life back on track, Keyaru decided to unleash a powerful healing spell that rewound the entire world back to the time before he began to suffer his horrible fate. Equipped with the anguish of his past, he vows to redo everything in order to fulfill a new purpose—to exact revenge upon those who have wronged him. [Written by MAL Rewrite]