"Zettai Ouja" to Yobareta Saikyou Dorei no Boukentan Tokihanatareta Dorei wa, Jiyuu ni Sekai wo Oukasuru

Gil has lived his entire life as a gladiator. He knows nothing but the kill-or-be-killed environment of the colosseum. He’s never had a friend. He’s never felt pleasure or satisfaction. And he’s fine with that. Really, it’s fine. Then, one day, a fire breaks out, ripping across the colosseum and burning everything in its path. As Gil walks through the rubble of his former life towards freedom, he finds he… kind of likes it?

Join a former gladiator as he discovers the joys and complications of a free life. Freed from his prison and let loose in a fantasy world of monsters and dragons, the former strongest gladiator is still ridiculously strong as a civilian!

(Source: Silent Manga Audition)