User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-34061653-20190104122109/@comment-34061653-20190104141203

Yeah but the thing is before Issei came along, people in Rias peerage weren't particularally strong except Akeno. Kiba was just mid class devil at best despite his years of training he had over Issei. Sairaorg is someone I can understand because of his past and how much he had to struggle but Balor Rias is already arguably stronger than his Breakdown the beast. In fact compared to Sairaorg BTB and Issei's Dragon Deification, Rias doesn't suffer from the side effects as bad as Issei and Sairaorg.

Issei only got to be as he is because he had help from outside sources. Even with Psuedo DxD, Issei needed a drink provided by Indra to increase the time limit while Rias and Vali could extend the time limit on their strongest forma tbrough regular training.