User blog comment:B214/Volume 23 discussion blog/@comment-30329599-20170319014445/@comment-10330822-20170319122420

At this point though Ultimate-Class isn't that strong though, relatively speaking. Issei's like Super Devil-Class/Heavenly Dragon-Class and Grayfia is Satan-Class. This means that Issei's "King" and "Queen" are also stronger than Ultimate-Class Devils. The secret to this fight is where do the teams mix in.

For example, Grayfia will probably have to fight Rias and Akeno so Issei can focus on Crom, because there is no way anyone other than Issei is beating Crom. Xenovia could probably hold Vasco using Durandal and Excalibur, but I'm not 100% she's beating him. That leaves Koneko, who I'm pretty sure isn't beating or losing to Rose, and Gasper, Kiba, and Valerie against Irina, Bova, Nakiri, and possibly Elmenhilde.

Valerie we don't know how useful she is in actually fighting, she may be no different than Elmenhilde except for the Graal. Which leaves Bova and Nakiri vs. Gasper and Kiba, and I don't think we know enough about their abilities to really say for sure right now.