User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-34061653-20190104122109/@comment-37560916-20190110223726

Man, it is highly coherent that Issei needs the pseudo-DxD to defeat them. Many people forget that the vast majority of secondary characters also evolve a lot as HSDXD passes, and that from the beginning it was said that several characters such as Kiba, Rias, Xenovia, Akeno, Sairaorg, etc. They are incredibly strong and exceptional. It is true that Issei has immense power and potential, but the others are not far behind, apart from the fact that several of them have trained a lot with Issei (For example Kiba, who is also a "technical" type, Issei's counter). As I said, it is completely coherent and demonstrates as everyone, not only Issei, they have been evolving (and will continue to do so) from the beginning, even the same author said it.

PD: Sorry if there is an error in my English, it is not my mother language.