Use Grim Grip to reel yourself toward his head and attack with your sword. Once the combos are done, use Grim Grip while still in the air. When his flames are gone, jump up to his head and grab it with the Devil Bringer. Then, once he lands from that, use Devil Bringer again to throw and punch him. After that, run away a small distance because he will release an explosion in the area around him. Make sure to pick up Green Orbs from the destroyed buildings and roll to avoid his flame geysers and sword attack. Continue attacking in this manner and use your Charge Shot to defeat him in under a minute.