How do say he's ruin characters and battle structures? Read this page.
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"One single swing of it's mighty tail could crush mountains and cause Tsunami's." ONE of it's NINE tails could do that.This was said on the FIRST page of the story.We have seen on many occasions that that Kyubi is a powerhouse and have heard throughout the story that Naruto would be if he were to ever gain control of it's power.So why are you surprised that Naruto is as powerful as he is and other characters who have power of not only the Kyuubi but other Bijuu are so strong? Plus Naruto has the Sage's power who is the God Of Shinobi - Kaguya has most of the power from all Bijuu and she is the Sage's Mom - he inherited his power from her yet her power level surprises you?
Like me guess what you're gonna bring up next.
"Madara was able to beat 5 Kages who are suppoused to be the strongest Shinobi in the world"
Madara was said to be the 2nd strongest Shinobi in history and that was before he was an Edo or had the Rinnegan and Wood style.