User blog comment:B214/Question and Answers 6/@comment-29362784-20161001024143/@comment-29963364-20161001055018

The very fact that Shiva was the one Azazel asked to deal with 666 if it revived, is proof that Shiva is the strongest God in the DxD series. The only beings that are stronger than him are Ophis (full power) and Great Red. And I guess 666 since Shiva himself said he could only fend it off for a time, not completely destroy it. Even went so far as to say that only Ophis (full power) and Great Red could destroy it.