User blog comment:B214/Volume 23 discussion blog/@comment-172.58.17.208-20170402060034/@comment-10330822-20170402165036

He's probably about as strong as Ajuka pre-nerfed. Remember, he still defeated Apophis who was Heavenly Dragon-Class, post-nerf. Ddraig and Albion were Top 10 material, meaning that if you are Heavenly Dragon-Class like that, who are probably close to rivaling Ajuka, who is also in the Top 10. However, its not really stated where in the Top 10 Ajuka is compared to the Heavenly Dragons, as well as the power difference between Ddraig and Albion, and Apophis. Crom Cruach is the only confirmed dragon that is equal to or beyond the Heavenly Dragons.

Either way, Issei trashed Rizevim, a Super Devil, just like Ajuka probably would have, so they can't be too far off from each other.