User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-73.46.6.122-20160203220433/@comment-26345952-20160205003351

Issei, in the devil society, is a Mid-Class Devil; but in terms of power in general he is far superior than this status.

I guess that in terms of power Issei at Vol. 20 has the power of an ultimate to a super devil (if not even higher if he can get used to and master the DxD form, but we'll see).

Issei in his base form is somewhat close to a mid class but with the boosted gear he can deliver high class devil attacks.

The balance breaker can put easily in High class devils, with Triana excelling High-class with the specific trait ( Magic, Speed, or Raw Strenght).

The Cardinal Crimson Queen is said to be (if tuned well) superior to Juggernaut Drive in some ways, and JD is known to unleash the power to surpass Maous and God. So CCQ is definitley somewhere around ultimate devil class, but not super (I guess).

This is all I can say for now since I'm not quite sure in some of my statements.