User blog comment:B214/Volume 23 discussion blog/@comment-172.58.16.156-20170402222541/@comment-31137559-20170403015407

Tiamat. Issei isn't an all powerful being yet. And DxD is OP. But only being able to maintain it for like 5 minutes doesn't make you OP. The form would be OP and you would be OP for the short while you were in that form. But Issei being OP overall. Yes he is. But no more compared to Tiamat at the moment.