1. Schwarzwald (The Big O)
Schwarzwald’s real name is Michael Seebach – a former reporter for Paradigm City, Schwarzwald works to expose the “truth” of Paradigm city and its inhabitants. However, he gradually became frustrated when Paradigm Corporation repeatedly censored his work. The search for the truth eventually turned into an obsession, and Seebach began to live a “double life”. For most of his life, he became even more obsessed with his work and cut himself off from human contact, including his wife and children. After having his face disfigured and bandaged like a mummy, Schwarzwald began his journey.
2. Kyoko (Is This a Zombie?)
Kyoko is a Masou-Shoujo under Ariel. She was originally introduced as a childhood friend of Orito, and also a survivor of a serial killer attack. Kyoko has always presented herself as a gentle and kind girl. However, she is actually a serial killer. Kyoto is a cold-blooded female samurai who likes to kill her victims for fun without showing any remorse.
3. Seryu Ubiquitous (Akame ga KILL!)
Yet another lovely-looking killer. Seryu Ubiquitous was originally a member of the Jaegers, formerly of the Royal Police. She is a girl who loves justice and righteousness. Although she initially appears as a kind, kind person, Seryu is actually cruel and mentally unstable. After the death of Ogre – Seryu’s superior and teacher, she felt very sad and suddenly thought that only killing was the best way to get justice.
4. Takami Minatsuki (Deadman Wonderland)
Minatsuki was just an ordinary girl before. However, one day, her mother abandoned her in an earthquake to Minatsuki’s surprise. This eventually led to Minatsuki becoming a person with a distorted personality and often lying. When Ganta first met her, she appeared as an extremely shy, gentle girl and displayed a very kind, caring personality. Her true nature is that of a sadistic psychopath, she even lied to turn her brother against her father and eventually killed the father.
5. Uryuu Ryuunosuke (Fate/Zero)
On the surface, Uryu Ryunosuke seems to be just an ordinary guy. But actually he has a very distorted mentality. Uryuu is haunted by death and its process. He thinks that people are inherently curious about death as a kind of forbidden knowledge and try to understand it by observing other people’s death, and creating a virtual experience, so that’s why he I became a serial killer. Uryu takes pleasure in these brutal acts. He mainly targeted women and children as they were easy targets. The victim’s innocence and poor self-defense make him feel his crimes all the more cruel and interesting.
Source link: Top 10 perverted killers that scare everyone in anime/manga (P.1)