User blog comment:IamJakuhoRaikoben/Chapter 466: Assassination, Review./@comment-1359322-20151216073212/@comment-4829046-20151216160005

None really, except for the bit that he lost an arm to one weakened Dragon(Dragon King, but still) while slaying thousands of them in his prime and with literally no sign of injury to his Dragon body despite being around for 400+ years. It is purely assumption, but it is unbelievable that a being deemed King of ALL Dragons due to having massacred so many, would be rendered unconscious for even that small amount of time by a Dragon that had a fraction of the power he had during the Wars. The War itself is another factor. What we saw was a 1-on-1, but these two Dragons had likely fought against armies of Dragons which possibly contained many other Dragon Kings. I know we have the "A beating B doesn't mean A beats C" but I'm using the Dragon logic Mashima has been conveying over the years. Granted, we still have so much to know about the Dragons and their systems and might never get any info on them unless we have a flashback arc so really, we could just pin it as Acno not living up to his own in-series hype. :P

I'm not trying to have an argument here though and I'm sure you are sick and tired of debates of this nature anyway Wrath >_<