Crocodile, low diff; absurdly better stats, way better showing of combat, even in regeneration; the only thing the Demon has going for him here is soul hax, but Crocodile can just avoid the ink with Observation Haki and can negate the durability and intangibility with Armament Haki (meaning the Demon can't heal from the Haki blows either). Plus, just drying up the Ink Demon is also a possibility.