Alright, I was just thinking and I've come to the realization that CxC Ise is probably not Satan-class until Volume 22 as a result of all his training and the effects of Dragon Deification. This also applies to Dulio, BxB Vali and Sairaorg.
So, if Dulio becomes High 6-C, Satan-class should scale above him. This post is long and isn't for people that have only watched the anime.
Also, I agree with Vergil that incomplete Juggernaut Drive Ise is stronger than CxC Ise. We know that the leaders of the Old Maou Faction are Satan-class with Ophis' snake because:
- Katerea easily erased Azazel's attacks after using it.
- Azazel was about to equip Balance Breaker against Crusceurey.
Shalba with Ophis' snake should be equal to them, but incomplete Juggernaut Drive utterly stomped him. CxC Ise has never stomped a Satan-class like this. The closest thing is stomping Shalba without Ophis' snake. Additionally, Juggernaut Drive used Longinus Smasher and could still go on, but it was not the case for CxC. It also makes sense because a complete Juggernaut Drive can apparently rival even Gods.
As for CxC Ise, he should be Ultimate-class before Volume 21 because:
- He said himself that he's Ultimate-class in power. I can't remember the volume.
- Sun Wukong said he was going to train Team DxD to take on Ultimate-class existences. If they were Satan-class, there'd be no need for him to say this.
- Yasaka is said to be Ultimate-class in power. Vritra Promotion Saji could somewhat fight with her, and Malebolge Vritra Promotion is much stronger. Yet, he lost to a Satan-class (Bedeze).
- Balance Breaker Sairaorg lost to Bedeze and couldn't affect his [Hole] until he used Breakdown the Beast.
- CxC Ise basically admitted to be inferior to Diehauser, and he also said it like the difference between them was big.
- CxC Ise couldn't do anything to old Vasco with his normal moves. This is important because Xenovia later overpowers him and their shockwaves were cracking CxC Ise and Saji's armors and causing them pain, so she'd be Satan-class if Ise is. Irina later fights on par with Xenovia.
- The members of Dulio's team at Rampage Ball are said to be Ultimate-class. If Xenovia and Irina were Satan-class, they would have stomped them, but that wasn't the case.
- After Xenovia uses Crimson Destruction Dragonar and Ise accepts her proposal, only then does she say she felt like she could take on a Maou-class.
- Only after Volume 21 does CxC Ise reach Grayfia's level (Satan-class), and he also beat Baraqiel. Because of this, we shouldn't accept Euclid's statement of him being as strong as Grayfia. It could be that he was equal to her before, but she has gotten stronger.
- Akeno erased one of Grendel's fireballs in his first appearance. Again, if Grendel and Ise were Satan-class, it'd mean Volume 14 Akeno is Satan-class or close to it, which doesn't make any sense. Xenovia also cut his fireball into little pieces. Though, I don't think that was Grendel's maximum power.
- Walburga can fight with a casual Dulio. Remember that Walburga wasn't exactly trying herself, and she also survived Ise's Crimson Blaster without major injuries due to her barrier. Additionally, Rossweisse's defensive magic circles stopped Grendel's casual fireball, but Walburga destroyed them with her flames.
There's probably more cases, but this is all I can remember for now. There are some things like Vali not being afraid of facing Azazel in Volume 4, but he wasn't afraid of facing Azi Dahaka in Balance Breaker, so...
Also, Cao Cao fought with an unserious Balance Breaker Azazel and pierced through his armor, but he knows their weakness and his spear can seemingly pierce through anything anyway.
Essentially, what I'm trying to say is that Satan-class characters should scale above CxC Ise before Volume 22. So, if Dulio becomes High 6-C, Satans should be "At least High 6-C".
Dulio only shows Satan-class strength in Volume 23.