User blog comment:FairyRaven/Fairy Tail Chapter 314: Erza vs. Kagura, Review and Commentary/@comment-4979627-20130112000400/@comment-5551986-20130112003837

But isnt the power of hatred the power of feelings? she wouldnt have hated Erza and Jellal if she didnt care about her brother, her love for her brother is what drove her to revenge. Love for lost brother = Feelings + revenge = superpower.