User blog comment:IamJakuhoRaikoben/Chapter 433 & 434: Ikusatsunagi & Demolition Fist, Review./@comment-5303512-20150511164336/@comment-76.161.172.226-20150511175003

Well, the last time the 18 battle gods came up, Erza and Kagura just kind of shrugged off the blast from up:

http://www.mangapanda.com/fairy-tail/312/14 http://www.mangapanda.com/fairy-tail/312/15 http://www.mangapanda.com/fairy-tail/312/16 http://www.mangapanda.com/fairy-tail/312/18

And that was before Erza started using Second Origin. That Natsu would be able to easily defeat one should be no surprise.