Controlling your own chakra throughout your body with great accuracy.
> Fire Ball Jutsu requires basic chakra control
> Walking on water or climbing on tries requires basic chakra control
> Kekkai Genkai users using multiple chakra natures requires great chakra control
*What Sasuke displayed in the Forest of Death with the Kunai on his foot was a form a chakra control.
Tailed Beasts and Jinchuriki control their chakra by balancing the ratio of yin and yang.
Hand seals are used for controlling chakra much easier.
Tsunade and Sakura focus chakra to their fist for monster strength, but that's not my point. My point is that Naruto needs a lot more focus to balance his chakra as he has a lot.
As I have already stated, the Rasengan requires insane chakra control because it is 'shape manipulation'
He took it a step further and worked on creating the Rasen: Shuriken. This is something that even Kakashi couldn't do and he was the one to invent the Chidori.
He later learned Sage mode and even perfected it, something Jiraiya failed at. This uses natural energy along with normal chakra. Blending natural energy with the users own chakra requires very high chakra control and focus, which is something that Naruto has achieved.
Kurama's power which he was able to control perfectly. This required a lot of focus to maintain high level of chakra. If you haven't noticed, boy, it takes a lot of chakra control for any Jinchuuriki to control their tailed beasts, so saying that it doesn't take immense control chakra to control a tailed beast is really dumb.
He befriended Kurama and awakened BM.
He could transmit and transfer Kurama's chakra and his own to every shinobi on the battlefield in perfect sync. Naruto can also fuse Sage Mode with Bijuu Mode to create BSM which is another feat with the Kyubi's power.
In conclusion, Naruto has been shown to be able to master his chakra control excellently.