User blog comment:Crimson and Darkness/Volume 24 discussion blog/@comment-95.90.224.203-20171105084734/@comment-31137559-20171106215404

In Volume 4, wasn't it stated that Vali could keep up his Balance Breaker for a whole week? Or was that the anime?

Either way Vali still has a vast advantage over Issei with his natural talent and immense demonic powers. And Issei above almost everyone in raw, destructive power. That doesn't make him stronger than everyone.