User blog comment:IamJakuhoRaikoben/Chapter 433 & 434: Ikusatsunagi & Demolition Fist, Review./@comment-24546844-20150511182459/@comment-25111584-20150511223240

Hmmm, true. In terms of raw power, maybe Igneel was more powerful than Acnologia. But ... that's all. Looking at all the soul taking things and all, Natsu might not just need to bulk up or whatever, but get some real good techniques too. 'Cause, despite his advantage in strength, Igneel lost to Acnologia fair and square as Acky never took outside help (that we know of anyway). So it wouldn't be wrong to say that Natsu would have to be better than Igneel to defeat Acnologia. Maybe not stronger but ... better.