User blog comment:B214/Volume 23 discussion blog/@comment-201.215.165.7-20170623220513/@comment-31137559-20170624115821

Sona is most likely Ultimate-class. She is very strong, but the main thing that stands out for her are her smarts and her quality as a king. She was already at the level of high-class devil at the beginning of the series. So it wouldn't be surprising if she's Ultimate-class right now. Sona's control of her demonic powers far surpass Rias', while Rias trumps Sona in the power category.