Koro-sensei

Koro-sensei is a character from the anime and manga Assassination Classroom (Ansatsu Kyoushitsu).
Description: A teacher in Class 3-E at Kunugigaoka Middle School, he is the story's main antagonist. He was once a legendary assassin nicknamed "Shinigami." He was betrayed by his student and sent to an antiparticle lab as a "lab rat."
Name: Derived from "korosenai" (殺せない), meaning "cannot be killed," and "sensei" (先生), meaning "teacher." Literally, his name can be translated as "unkillable teacher."
Some abilities: has a keen sense of smell, hearing, and vision; regenerates limbs, body parts, and internal organs. Can easily catch bullets in flight, deflect them, and quickly intercept weapons.
Plans: Plans to destroy Earth once he finishes teaching Class 3-E for a year. An octopus-like artificial creature, approximately three meters tall. It has a large, spherical head with a wide grin and small, beady eyes. It uses two pairs of tentacles as arms, while the remaining tentacles serve as legs. Korosensei has a pair of hidden nostrils, making it appear as if he has an extra pair of eyes. He wears a black academic robe, a small black square hat with a yellow tassel, and a black tie with a yellow crescent moon on it, which was a gift from Yukimura Aguri.
Koro-sensei's complexion changes depending on his mood:
Yellow ~ Normal state
Yellow and Green Stripes ~ Complacency
Orange and red circle ~ "Correct"
"Purple and a cross all over the face" ~ "Wrong"
Pink ~ Sleepy, embarrassed (blush appears on cheeks)
Purple ~ Shock/Panic
Blue ~ Sadness
Red ~ Irritation
Black ~ Fury
Gray ~ Confusion
A pervert BUT doesn't let other people spy on other girls, especially if the girls are under 18. ESPECIALLY if the girls are from his class.