User blog comment:Panemorfos/Strongest Fairy Tail characters up to chapter 470/@comment-26523876-20160130221513/@comment-26271908-20160131095807

The list, as the long I've seen, is based on raw power rather than skill or ability. Juvia didn't defeated Keith using pure magic. She used an strategy that could have costed her life, but before using her mind, her magic was not match to Keith's powers

I think that Lucy is more powerful than Ultear now, considering how she aged and this might have affected her powers and how Lucy trained and is now more powerful (Taurus Dress feelings). Juvia is weaker than Lucy. If not before, certainly is now. Lucy's magic is extremely diversed and the right use can lead to a giant battle advantage. However, before the Avatar arc, Lucy never realized the potential and just picked up a random key and summoned a random spirit. Now, she knows (More or less) how to do this right

But I agree that Rustyrose is weaker than Keith