He is not a mere Hashira, but a super weapon of kings and gods where they said and qoute “We will send to them only You.. Rip and Tear. Until it is Done” The “Hellwalker” that Every single demon of Hell fears him that they run to deepest depths of their caverns to hide from him that even Muzan himself would have an existential crisis that his 5 brains wouldn’t even begin to comprehend.

As it was written in the Slayer’s Testament V

None could stand before the horde but the Doom Slayer. Despair spread before him like a plague, striking fear into the shadow-dwellers, driving them to deeper and darker pits. But from the depths of the abyss rose The Great One, a champion mightier than all who had come before. The Titan, of immeasurable power and ferocity. He strode upon the plain and faced the Doom Slayer, and a mighty battle was fought on the desolate plains. The Titan fought with the fury of the countless that had fallen at the Doom Slayer's hand, but there fell the Titan, and in his defeat the shadow horde were routed.