Acnologia is 400+ trigger dragon , FT manga had lazy fights and nonsense. FT verse can beat Naruto , One Piece and DBS. I know is crazy but it is true because in FT verse had potential that can surpass big 3. Let explain seriously , 12 spriggan was powerful empire and even bigger than four emperors. There are 12 mages who were around God Serena's lvl. Their magic made scare FT and Natsu too, Brandish had a magic that can wipe out an island , Dimaria magic is time. Time magic is dangerous because it can wrap it to slow down or pause world's time. We haven't seen Dimaria full power if it was she could wipe out the world.God Serena was the most powerful wizard saint , he had 8 dragon slaying magic ,remember DS magic is made to kill dragons. His magic had more than two slaying magic in which can hurt an enemy. God Serena wasn't using dragon scales of DS from 2nd generation when he fought four gods of Ishgar. Irene was the creator of DS magic , she summoned a meteor from space that can destroy a continent , weather maniputlation , enchantement magic ,possession magic and her own DS slaying and also she 400+ or slightly older than Acnologia. August was the general of 12 spriggan and strongest mage of the group , he had knowledge of magic and mastered most of them. I would surprised if August learnt quicly FKD spell and he can copy any magic, He can even do Hakai easly , use Jiren's technique , do kamehameha hahahahah.
Don't get me wrong, I completely respect your opinion, but I just happen to look at it from a different perspective.
In my opinion, the Spriggans showed
zero potential in the last arc. They were purely based on hype, which is fine for the "prelude to war", but that flaw eventually became ridiculous later on in the arc.
Team Natsu being "scared" of their magic power just serves as a good initial hype tool, but it was eventually shot down when the other Spriggans underperformed in battle.
Once Natsu became serious, he was easily able to turn the tables around on people the likes of Brandish, Dimaria, Jacob, and Neinhart.
The same goes for other Ishgarian characters like Gildartz and Gray.
The only Spriggan who I believed actually lived up to his hype was August. He fought directly on par with Gildartz, who was arguably Ishgar's strongest wizard. I admit, that's definitely worthy of praise, even for the "General of the Spriggan 12".
Some of the other Spriggans also had decent or acceptable feats, but it was nothing extraordinary as we were led on to believe initially.
Overall, the amount of wasted potential was far past what I would call "the limit".
Acnologia and Zeref were indicative of that, especially since their downfall
did not match their given circumstances.
