I was NOT familiar with Diablo's game (Vol. 13 spoilers)
Finally entering the war arc, the strength dynamics have been completely flipped on their heads. You have no clue how strong the enemies are, and no clue how much grow the forces of Tempest have made. I've always glazed Diablo since day one, but recently he hasn't had any action outside of washing Rain (bleu) and comments about him being weak to insects like Razul and Zegion.
AND THEN, this guy pulls up two the Armored Corps Command Center with the BODIES of two single digits?! The same people that Benimaru and CHLOE were struggling against.
I've felt that until recently (~Rosso arc ending) that Diablo was stronger Rimuru, but is it fair to say they might be equal as tempest's strongest right now?
(not including veldora)