You mean the Full Kirama that was being controlled and is said that Bijuus are stronger as Jinchuurikis who can better focus their power? Yang Kurama was out-low on chakra, borrowed some from Yin Kurama then both Naruto and Minato gave the alliance chakra that's comparable to Hashirama's chakra volume. Plus Naruto is like 10 years older than he was when Kakashi said Narito surpassed the Hokage.