User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20170323170829/@comment-10330822-20170324141033

If I were him I'd either ask to be made a "Great King" or change the rule that prevents Maou from having harems. Right now, I'd say the latter is his biggest challenge to becoming a Maou, if that is what he wants to do in the future at some point.

If not those, I'd wish for Dulio's wish to come true. I feel Issei's out to prove himself, Dulio's wish is a worthy cause, so he might just go along with it even if he beats Dulio.

Otherwise, I feel Issei most has everything he could ever want, except maybe Tiamat's treasure that Crimson was talking about. XD