Mata Nui is not a Great Being. He's not even the Great Spirit anymore, save his name. Even so, if Mata Nui is a Great Being, Metus wouldn't know unless Mata Nui told him, like how no one knows that Velika was a Great Being.
I would have to say Tuma (in the movie) and Metus (in the movie). Tuma, just a really weak big bad guy and Metus was just annoying; he was an agori who didn't think twice about messing with a Great Being.
Oh excuse my mistake!
And yeah I guess if Metus knew, maybe he mightve not done what he did.
BTW: Dam dude your at 300 posts?!?!
Thinking about it, yeah, Tuma.
He didn't do anything in story aside from get absolutely owned by a gravity-defying (look at those jumps!) Mata Nui, compared to past big bads like Teridax, Roodaka, etc.