Shinako

You can take it how you will but when I thought of that I was also thinking about all the feats and statements we have to Acnologia's name according to the manga/anime so I could compare him to Vegeta in both his base and his Great Ape form. Zeref is an immortal wizard and is considered one of the most powerful wizards in history but he is scared of Acnologia's strength. The entire  war was to get to the Fairy Heart which was the only way Zeref could see himself winning against Acnologia.  That thing not only supposedly gave him unlimited magic power but also the ability to control time and space as if he were a god. 
          
          https://meo.comick.pictures/14-_9AGBcjjoaDOF.png
          
          And he could also just erase the current world in place of a brand new one. 
          
          This is even hammered home when Zeref tells Acnologia that he could take over the entire world with his overwhelming strength and this was after Acnoliga ripped his arm off. That meant losing his arm didn't lessen his strength at all. It was inconsequential to him. 
          
          https://meo.comick.pictures/5-mK9p5GtXYYHS-.png
          
          https://meo.comick.pictures/6-ihHrZosU_0QwT.png
          
          The same thing was said by Vegeta in the manga where he said he came to Earth on that day in case he wanted to use his transformation to wipe out the planet quickly if he needed to. 
          
          https://meo.comick.pictures/5-dgjr_O9e_kEt-.png
          
          Seeing that these two statements are kinda similar there's no reason to totally disprove that Acnologia could be as strong or even stronger than Great Ape Vegeta or that he could even wipe out the planet
          
          https://meo.comick.pictures/10-eftjBqVGhbaDw.png
          
          And in the realm of Fairy Tail, Acnologia would have a much easier time since he's immune to all forms of magic since he can just eat it and get even stronger. 
          
          I can see your point when it comes to battle IQ and skill.  But this all just my own speculation when using the series as a guide and my own opinions. Had to type here since I couldn't in comments. Hope I didn't sound rude