User blog comment:FairyRaven/Fairy Tail Chapter 363: The Stories That Demons Read, Review and Commentary/@comment-1153699-20131207173113/@comment-7418318-20131208182614

But Gildarts also said that Acnologia was barely showing a fraction of the power with which it mauled him in the fight against Makarov and later the entire Tenrou team. Not to mention the power we did see Acnologia display when it "destroyed" Tenroujima.

The Dragon was just toying with them, so we really can't judge from that particular fight.