It's not Kamina. Presumably, it's the embodiment of Spiral Energy itself, which drives the Dai-Gurren Brigade to do the impossible, see the invisible, and yes, fight da power!
First, at least let me admit that I'm a little butthurt about those haters that only know about Demonbane thanks to TV Tropes, going around hating on Gurren Lagann because it got popular or whatever reason they have. Second, what truth? You just posted Demonbane's abilities. It doesn't necessarily prove that Demonbane is superior to Gurren Lagann. Now let's just say both of them were rolled up by a Katamari before this turns into a silly flame war.