Tomoo

Tomoo is a minor villain in the anime and manga series Elfen Lied. Tomoo served as the chief force that ultimately turned Lucy into a homicidal maniac, and he's also the reason for her deep hatred of humanity.

Biography
Tomoo was an eleven year old boy who was the ringleader of a group of nameless bullies. His favorite victim was Kaede. He and his acquaintances endlessley taunted her and bullied her because of her bottling up her emotions, and called her hideous names such as "Oxen" because of the horns on each side of her head. Tomoo mainly targeted Kaede, because he wanted to see her express some emotion from all of his attacks.

One day, Lucy meets a young girl at the orphanage, and befriends. It's unknown if the girl befriended Kaede because she genuinely felt sorry for her, or if Tomoo set her up. Whatever happened, the girl tells Tomoo that Kaede had a puppy that she was taking care of, and the other boys present Tomoo with the puppy. Tomoo then teases Lucy about the puppy, and then proceeds to throw it hard against the wall. He then grabs a vase, and then beats the poor dog with the vase and continued to do so until the poor animal stopped moving. Kaede had finally had enough of her tormentors, and she proceeds to use her invisible vectors on them, and she slaughters them all. Tomoo was the last one that was killed.

The influence that Tomoo had on Lucy continued even after he had died. Tomoo would often be manifested up by Lucy whenever she felt great stress. He would always be mocking her and calling her names. Ultimately, Tomoo is the one who was responsible for Lucy's descent into madness, and he was the one who molded her into a serial killer because of his influence.

Personality
Tomoo was considered a very cruel and monsterous figure. Unlike the other bullies who only helped to kill Kaede's puppy because they were most likely forced into it, Tomoo was the only one who was the most self-aware and knew what was right and what was wrong. He killed the dog knowing that it was destroy Kaede, because that dog had served as her only friend during her miserable existence. He's also a very sadistic individual. When he was killing the puppy right in front of Kaede, he's shown clearly sporting a look of sadistic glee on his face. These traits most likely would've made Tomoo become a serial killer had he grown up if Lucy didn't kill him out of anger for him killing her pet. Even though other villains in the series may as well as overshadowed him in terms of heinousness, Tomoo has managed to make himself out as the most evil character in the series, as well as the most hated villain from the show, or anime in general as well.