Well the closest thing Naruto has for focusing chakra is shown when he was learning rasengan, he had to focus a lot of his chakra at a single point, this took focus and concentration
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. It was the leaf concentration training where you focus all of your chakra into the left that Naruto used to master the 2nd step of Rasengan
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Well Shizune said Sakura reached her (Sakura's) pinnacle, that's her highest and not the highest in general. After all Tsunade came and fully healed Shikamaru with a touch of her hand when Sakura couldn't so you can still see Tsunade's pinnacle is higher than Sakura's. People like Sasuke and Naruto only keep improving so their pinnacle isn't close, Sasuke have been said to surpass Itachi, Nagato and EMS Madara while Naruto has been compared to Hashirama 4x and to the Sage by the Bijuus.
being able to break that one A visual genjutsu doesn't mean she can break other A rank genjutsus. Look at Kurenia, a jounin who specialize in genjutsu got her genjutsu reflected and had to bite her lips to break out instead of breaking out by disrupting her chakra.
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Her description on her genjutsu skills: The full extent of Kurenai's abilities are predominantly unknown. But, her skill with genjutsu is so vast that it is said to rival even those of Itachi Uchiha.[2] Most of her techniques focus around flora; primarily using large trees to bind opponents as well as flower petals for various reasons. She is also able to simultaneously affect multiple opponents with her techniques, as seen during her fight with Kisame Hoshigaki and Itachi Uchiha. Itachi, a genjutsu master himself, has also praised her skills.[14] Furthermore, she could revert the effects of genjutsu to the caster.
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