Assassination Classroom

An inhuman nigh unkillable creature has decided to destroy the earth in less than a year. For some reason he has decided to become a teacher and under no circumstances will harm his students. His students now have to kill their teacher before he destroys the planet.


 * Kryptonite Is Everywhere: To be fair, the threat that is Korosensei is a closely guarded secret and anyone other than world leaders let in on that secret is more likely than not supposed to kill him and has been supplied special weapons suitable for the sole task of killing him (in fact often these weapons are unsuitable for killing humans).
 * Detonation Moon: And earth is next if Korosensei isn't killed soon enough.