User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-185.112.105.215-20180606133805/@comment-217.136.96.176-20180608093852

Rias is stronger by combining her power with Gasper or Issei, but it would not be her power. Everyone is growing stronger, not just the Gremory. Of course, in terms of power output, she would be above Riser as the power of destruction is several times more powerful in terms of destructive potential than a same amount of demonic energy from another devil.