User blog comment:Crimson and Darkness/Shin DxD 3 discussion/@comment-41.13.12.215-20190801100529/@comment-10330822-20190804013416

I agree in this regard. The problem with Vali as a rival is that while his development as a Dragon Emperor certainly kept pace, I don't know if DxD L really qualified as keep Vali on track with Issei's DxD G. Because there is no real comparing the power of Ophis' Infinity to the power of Lucifer, its clear one is far below the other. Rather, it keeps him on track with Pseudo DxD more like, where the maximum Issei's body can handle right now through Pseudo DxD matches the hidden potential realized in Vali through DxD L. The truth depth of Issei's power is probably beyond Vali, and we will probably see that when Issei uses AxA and ExE.

Of course, in Vali's defense, the story does have some wiggle room.

Imagine this for a theory, Lilith, Vali's great-grandmother, has been experimented on as part of a purpose to create a new breed of pureblood devil. And has already succeeded in creating what is theorized to be a Dragon God-level pureblood.

What if instead of his great-grandfather's heritage or Albion, Vali's true power may lie in his connection to Lilith, and Vali might be able to harness this strange result to achieve Dragon God-level power himself. Which will be required if we are meant to take their final battle seriously.

After all, Vali is slowly be surely being left behind. It has already been explained that Issei's soul is undergoing a change due to the Dragon God Aura of the Pseudo DxD form. Meaning Issei very well maybe adapting to his power as he continues to use it, and when Ophis and Lilith, the Dragon God, come to "cooperate" Issei's power may fully be unleashed as a Dragon God.

Whether this is will fact into AxA and ExE isn't really clear, but it goes without saying that the way they are building up Issei's power, he eventually have no equal.