User blog comment:B214/Volume 23 discussion blog/@comment-31764731-20170418200747/@comment-201.19.110.59-20170418235442

I do not think Issei can beat any of the top 10 strongest beings in existence, in full dxd mode he still had some difficulty to beat rizevim, and he needed to use dxd mode to beat barakiel that is not even close to him. Top 10, as for vali, he received ophis powers in the same way as issei, and we do not know if he can or can not use that power again