User blog comment:B214/Volume 22 spoilers/@comment-64.237.231.92-20160722012904/@comment-26926813-20160722150323

'''But Apophis was Heavenly class and Issei defeated him. So doesn't that make issei the same as Vali ?? '''

Iseei's DxD form was nerfed in the end of volume 21. In full power of his DxD G he must be stronger than Vali because of Inifinity Power of his DxD G form. Vali's DxD L form doesn't have it. But nerfed DxD G of course much weaker than DxD L. Nerfed DxD G must be on God lvl, but not Heavenly Dragon lvl