I Was the Final Boss

Baphomet is the ruthless, dispassionate lord of the Abyssal Tower, a mysterious, monster-filled dungeon plaguing the human world. Many Hunters seek to defeat him and bring the tower down to no avail. Despite his demonic power, Baphomet grows curious about humanity. One day, Baphomet is defeated by Raven, the strongest Hunter, and realizes that his true wish is to be just like the humans he previously looked down on. In death, he is granted his wish, as he awakens as a human – without his powers!

(Source: Webtoon Entertainment)