User blog comment:B214/General Discussion/@comment-29963364-20161114220214

I just had a thought about Issei's DxD G form.

What if the "Infinity" he has in this form (and of course Ophis herself) is just a quality of their power, and not that they are infinitely powerful?

Something like this:

Issei/Ophis has a set "power level", but their "Infinity" makes it impossible for their power to run out, or for it to be canceled, halved, obsorbed, etc.

This might explain why Issei could hit Rizevim and Apophis when he used the DxD. "Infinity" can't be fully "canceled" (Rizevims [Sacred Gear Canceller]), and it can't be fully "dissolved" (Apophis' darkness).

So what makes Ophis (and Issei's DxD) so powerful is that no matter what defenses or resistances the opponent has, they will take the full damage of their attack.