Failure Frame: I Became the Strongest and Annihilated Everything With Low-Level Spells

In the world of Fantasy, Mimori and his classmates became heroes one of the goodness there. They got powers and all of them have great abilities that they use to save people in that world. Mimori got a single power of E-Rank that was not now even useful at that time. There is a dungeon from where no one came back alive. He went there and there he found his power abnormal and got the ability to defeat the rago n in the dungeons which made them popular.