User blog comment:Way2manybeer/Special war potentials/@comment-4822693-20130704131627/@comment-11051098-20130714225535

Yamamoto was the strongest Shinigami the past 1000 years, roughly the entire existence of the Gotei 13. I don't think the RG members are stronger than him, but at least some of them can very well be close to his level of power.

And Yhwach stated Yamamoto was more powerful 1000 years ago than what he was for the whole storyline of Bleach as we have seen, so it is possible that some RG members can be as strong as we have seen him now.