The Strongest Warrior Goes To School summary:

Seok Hyun-woo is frequently bullied by the troublemakers at his school, who love to take advantage of Hyun-woo’s poor circumstances. Hyun-woo toughs it out though and continues to endure this frustrating situation. This all changes though, when on one (un)fortunate night, Hyun-woo is beaten and embarrassed by the bullies, with his spirit being pulled from his body shortly afterward. Coinciding with this odd occurrence, a bizarre abnormality takes place somewhere else in the vast universe… Due to that bizarre abnormality, the spirit of Hyun Woo-seok, a powerful warlord from an alien planet, is forced into Hyun-woo’s body. Woo-seok, now a powerful warlord in a moody highschooler’s body, swiftly and easily overpowers the bullies… In his head, however, the bewildered Woo-seok has just one question: Where the hell am I?! The bullies, unaware of what’s happened to Hyun-woo, begin planning their vengeance. They do this, even though they were the ones picking on him in the first place… Seriously? It’s time for this alien warlord to dish out some payback on these sneering pricks!