User blog comment:B214/Volume 23 discussion blog/@comment-1359322-20170519103917/@comment-10330822-20170521044152

You are missing my point though, even Sirzechs and Ajuka are no match for Great Red and Ophis. That is what I am saying, even the exemplars of Devil society are not a match for the power that could potentially manifest from Issei, and, unlike Vali, we have confirmed that Issei has *two* additional modes beyond what he currently has, which is roughly equal to what Vali currently has.

Also, Vali isn't a Super Devil, he's a descendant of Lucifer, that is where his power is coming from. Issei already killed/defeated half a dozen devils with "immense demonic power", its actually not that special at this point. Whether he develops into a Super Devil or not is irrelevant, because we are talking about his power he got from "Lucifer" who Sirzechs and Ajuka both surpass.

Now, if Vali got his power from Sirzechs, you may have a point there, but he gets it from Lucifer, who is clearly inferior to both Sirzechs and Ajuka. Now, he might develop into a Super Devil like Rizevim, since it is in his bloodline, but saying that makes him better than Issei is a real stretch. Issei is about as close to a dragon god as you can get while not actually being one.