Diavolo

Diavolo is a special boss that only appears on the second playthrough and up. Like Emporio's Room, he is hidden in a different spot in almost every location on both paths. When you find him, answer No to his question to battle him. While he can be battled at any point the game, doing so early on in the game is not recommended unless you are using a Stand that has experience from a previous playthrough. You will want to wait until at least Calcutta if the rest of your party's experience carried over, or the Fishing Village if not. He has a chance to run away, and if he does, he will disappear from the map, but you can fight him again by entering and exiting a building.