I'm seeing a lot of nonsense from the comments addressing combat in OP.
Naruto's battles are scaled to be somewhat believable.
And the battles in OP aren't ?
where as OP everything is so over the top it ridicules the serious tone it attempts to present.
Oda rarely betrays any of the parameters he set in the manga regarding power levels. It is also hilarious to say that it is a bad thing that OP is over the top ( It is pretty tame. Shit, just look at Toriko )
when Nardo characters are currently blowing up country sized areas casually.
When it comes to power levels OP is actually pretty logical. There isn't a colossal power discrepancy between the top dogs of the manga on the pirate and marine side, meaning that they are all a threat to each other making the Yonkou/Shichibukai/Marines power triangle possible.
Think about WB and then take a look at characters like Madara and Aizen.