Naruto Shippuuden Episode 42

[Killa-Eyez]

While I don't really disagree with this statement I'm not completely sure the Kyuubi could pull off that particular move if not for Naruto or atleast another source of chakra. The reasoning being those blue balls were not Kyuubi chakra and it seems odd it would have used two types like that if it didn't need to do so. As such I assume the blue balls are actually Naruto's natural chakra as its always been shown blue with the Kyuubi being red instead.

Purely speculation of course as we have no way to prove or disprove it,

While it's pretty obvious that the blue chakra is Naruto's and the red the Kyuubi's, I still really don't think he would've need Naruto to do the move... He could've just used his own chakra instead of combining it with Naruto's. He prolly used Naruto's because the Kyuubi is not in his original state, meaning he doesn't have his usual amount of chakra making Naruto's chakra usefull to make the blast a little more powerfull.
I seriously doubt he would need Naruto for this. Though all I'm stating is not fact, just based on what I see in the anime... I think it's time for me to finally read the manga.

Give me a break. Oro was even less serious in his fight against the Third. Maybe the moment when his hands began to rot he was serious for the first time in that fight. Before that, he just smoked his cigars at leisure while the Third was fighting against his deus ex zombies.

And it surely didn't seem to me like he would have had any special ways to immediately defeat four tails. He didn't have any super zombies at hand and as we saw the mini-kyuubi was perfectly capable of disintegrating anything it touched. Oro was never in any truly real danger because he could have withdrawn at any point as the kyuubi was content at standing still, but that doesn't mean defeating it would have been that easy.

Kay, Oro might've not been that serious against the Third, but he was serious enough to get him killed... Also the Third was weak, and he was fighting his formal desciple and the mixed emotions that comes with that. That just made the work for Oro easier. So if he would get truly serious against the Kyuubi...

Kay, he might not have defeated the Kyuubi with ease, but defeat him, I think he would've. I'm not talking about killing the Kyuubi but I'm sure Oro's got a couple of sneaky Jutsu's up his sleave. Oro up till now has been a great example of a Ninja. And I think a Ninja isn't just about killing each other, but to get their goals accomplished using any means necessary. Oro would do just that.

He said best battle in Shippuuden, not best battle in Naruto.

I think using "Naruto" he meant both Naruto and Shippuuden, as a whole.