A dark laboratory. A piercing scream. A grinning scientist hovering over their intended victim. These are some of the images that come to mind when the subject of human experimentation comes up. There are a surprisingly large number of anime characters who went through human experimentation. Everyone knows about Nina Tucker, whose father fused her body with a dogs' in Fullmetal Alchemist, but that's not the only example. In Tokyo Ghoul, Ken Kaneki is the victim of a scientist who uses him as a prototype for artificially created human/ghoul hybrids. In Charlotte, Kazuki Tomori is driven mad by the pain he endures at a scientist's hands.
These are not stories of people who willingly signed up for safe and ethical experiments. These are stories of people who were forced against their will to endure excruciatingly painful experiments which left them with permanent physical and emotional scars. Some of these stories are disturbing, so read on at your own risk.
No list on human experimentation would be complete without the tragic story of Nina Tucker. Not only was she the subject of a brutal experiment, but the person responsible for her suffering was also the man who should have been most invested in protecting her: her father.
In order to keep his job as a state alchemist, Shou Tucker produced a "chimera" that could speak. While that earned him some acclaim, he still needed another chimera - and he got one. How did he accomplish this difficult task? By fusing his daughter with the family dog, creating a being that could not enjoy life as either a little girl or a dog. This wasn't the first time he'd done such a terrible thing - the first chimera was a fusion of his wife and another dog.
While Tucker doesn't have as many victims as some of the other evil scientists discussed on this list, the fact that the victims were so close to him makes him one of the most reprehensible anime villains of all time.
Lucy is a Diclonius, which means that she's a humanlike being with a few key differences: namely, her horns and her psychokinetic abilities. Due to both her status as a Diclonius and her tendency toward violent rampages, Lucy is held captive in a laboratory for three excruciating years. There, she endures painful experiments at the hands of unscrupulous scientists. Already inclined toward destroying humans, she eventually escapes by tearing the place apart and taking the lives of every scientist or guard who tries to get in her way.
The Abyss is a gaping hole in the ground that's incredibly difficult to study because everyone who ventures down there is hit with the Curse of the Abyss when it's time for the ascent. Once you get to the bottom of the Abyss, the curse can cause severe symptoms like agonizing pain, loss of humanity, and death. Scientists are always looking for ways to counter this, and a man named Bowndred decides to trick a group of orphans into a fatal experiment.
The only survivors of the experiment are Mitti and Nanachi. The two of them are sent down to the sixth layer of the Abyss in an elevator designed to push the curse onto only one person, allowing the other to survive. Mitti takes the brunt of the curse and transforms into an inhuman being with few cognitive abilities. Nanachi's body transformed as well, but it wasn't as dramatic. After that, Nanachi is forced to work for Bowndred while he repeatedly destroys Mitti's body to see how many times she can reform herself - since the curse has made her more or less immortal. Nanachi eventually runs away with Mitti on their back.
When Crona was a small child, their mother Medusa replaced all of their blood with a substance called Black Blood. The Black Blood was combined with a melted down magical weapon called Ragnorak. While this gave Crona a wide and impressive range of supernatural abilities, it was also a painful process for the newborn to endure. Also, Medusa wanted to use Crona's abilities for her own nefarious purposes, often forcing the child to take lives and punishing them with isolation and abuse if they refused.