Shiro (Assassination Classroom)

Shiro,alias Kotarō Yanagisawa is the main antagonist of the Japanese Manga and Anime series Assassination Classroom. A cruel and vengeful scientist who bears a deep grudge against Koro-Sensei because he was the one who stole evertyhing from him.

History
Before the start of the series he was a scientist who was testing and using an assassin called God of Death in order to create an anti-matter being, however when the experiment was going smoothly, he witnessed the transformation of the assassin which killed his fiance and destroyed his lab.

Enraged by the fact that he lost everything, he swears revenge against the latter stating that in the end he will pay for his actions.

He disguised himself with white robes and changed his voice through a technologic device, he later found a kid named Itona Horibe and used him to kill the responsible of the incident, which is now a teacher with the name Koro-Sensei.

When Itona failed for the third time Shiro realized that he is weak and useless, so he abandons him and states that he will return.

He reappears again at the end of the second semester and he is given custody of the defeated second God of Death, he tells him the identity of Koro-Sensei and offers him a final occasion to kill their teacher by the end of March.

He transformed God of Death (and later himself) into a tentacle monster for the final battle against Koro-Sensei, but he is sent by the latter towards the anti-tentacle barrier which disintegrates him to nothing.

Appearance
Before the incident he wears normal scientist clothes, after the incident he disguised himself with white vests and a masks over his face, which later drops and reveals his short, wavy black hair and his prosthetic left eye.

Personality
Before the incident he showed to be arrogant, amoral and abusing towards his coworkers and even his fiancee, after the incident he became extremely manipulative and states that he can willingly take his own life in order to kill the creature which ruined his life.