Tail of Rot to Steel

[Yes, I meant Tail, not Tale. Not a typo.] Everyone in class received a divine gift.Kazuya, the guy who stole my childhood friend and made my life hell, was crowned SSS-rank Hero by the gods themselves.Me?They branded me F-rank trash and abandoned me in the world's strongest dungeon to die.No hidden power awakened.No goddess took pity.No system glitch turned me into a secret overlord.Just a discarded weakling.and the monster I'm prepared to become to drag that "Hero" down from his throne. [Can a tail of rot, turn to steel?]