I want to know the chakra nature(s) of the Nine-Tailed Fox, Kurama. Not the chakra nature of Naruto, I already know that. This is all I need to know.
According to Narutopedia, the anime version specifies both fire and wind natures.
The reality is that the Bijuu are just a huge mass of chakra, and specific elemental natures don't really matter when you're dealing with chakra at that magnitude.