User blog comment:FairyRaven/Fairy Tail Chapter 363: The Stories That Demons Read, Review and Commentary/@comment-1153699-20131207173113/@comment-4829046-20131211081427

I find it pointless to think about who is strongest anymore cause even if you take magic incompatibility and skill into the equation, the moment you bring in plot-armour/convenience and nakama power, everything becomes nonsensical even though it is enjoyable to watch someone getting beaten to kingdom come. But I do hold high hopes for Acnologia and Zeref(when dead-serious) as well as Mavis(when alive) as the strongest characters in FT. Igneel might also be added once we know for sure where he stands in relation to the power scale of the strongest dragons.

And in my book, the strongest character in the series would be the one who forces Natsu to go into Perfect Dragon Force mode and require the largest amount of nakama power evah to defeat. Afterwards, Natsu will just go back to being Natsu. Getting beaten up by the other guild-mates at varying times. We shall see.