User blog comment:Miskos3/Fairy Tail 522 & 523: Gray's Trump Card & Is Destiny Burning, Review/@comment-184.178.44.233-20170220001908/@comment-203.215.123.130-20170220052029

Maybe it's something more than simple imitation of what he sees others do, but perhaps stems from his profound understanding of magic to the point that he can 'simulate' any spell that doesn't involve special items or requires magic power greater than what he already has. Then again, that would be way too overpowered for someone who isn't even the main antagonist.

The other thing I've noticed is that although August finds certain magic types 'interesting' (maybe because he didn't expect the other wielders to have them as well), he only expressed shock and worry upon seeing raw physical prowess (in the case of Acnologia finishing off God Serena), destructive power (in the case of Gildarts destroying the cathedral), or when he's outmatched in a physical attribute (in the case of Gildarts blindsiding him).

I think a reasonable way for August to be defeated in battle would involve him being physically overwhelmed or incapacitated, or him being hit by raw magic power that he can't control. Sadly though, it's more likely that he'd fall because of a surprise character flaw, or because of a secret magic that he cannot counter...