User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-85.154.145.2-20140120193118/@comment-1359322-20140120235059

Despite so, Issei still can't become a Super Devil. His potential aside, Issei isn't a pure Devil nor does he possess any special or powerful Demonic powers. So him reaching a Super Devil is just like a dream. He might be able to become something like a Super Dragon though.

The one with the potential of being a Super Devil might be Vali, but he's still a Devil hybrid.