FFF-Class Trashero

Hansoo Kang was an average boy living in the normal world when he was suddenly summoned to Fantasia, a fantasy world run by demons. Deemed the Chosen Hero, he's spent the last ten years building himself up to defeat the lord of Fantasia—which turned out to be a piece of cake. As he eagerly awaits his return to the real world, the "god" of Fantasia appears and throws a wrench in his plan: a report card that reveals there's more to being a hero than just might.

(Source: Tappytoon)