Sword and Sorcery: A Killer's Job Is to Slaughter the Whole Family
The Song of Fuck and Kill
As a killer, Fa Ke Mang Si Te conscientiously carries out every assignment to wipe out an entire family. His hands are stained with endless blood, and for years he has topped the continent's most-wanted list.
As a student, Fa Ke Mang Si Te is always respectful toward his teachers and kind to his friends. His friendly, approachable nature makes him popular with both his classmates and teachers.
Then one day, he kills one of his classmates...
“My name is Fa Ke Mang Si Te, codename [Black Devil]. As long as you don't discover who I am, you can keep addressing me pleasantly instead of calling me a monster bastard.” Pulling the bloodstained knife from his classmate's chest, the monstrous bastard Fa Ke Mang Si Te said this.
It's pretty good. I don't think the protagonist is a good person.