User blog comment:Sinister 00/About 666/@comment-25136646-20140711174634

The final battle will certainly be against 666. But who is going to fight him? It might be Great Red since he's the only being who can match 666. However, perhaps he lost some of his powers by giving them to Issei?

I have a theory. Have you guys saw Beyblade Metal Fury? The Legendary Bladers fought against Rago and the God of Destruction Némésis. When Némésis revealed to be too powerful, the protagonist Gingka Hagane fought in the last battle against Némésis to save the world.

What if something similar happens? Perhaps the 13 Longinus possessors will fight 666 and when 666 will eventually become too powerful, Issei and Great Red will team up and fight 666. What are your opinions on the final battle vs 666?