Originally Posted by Whiskey Tango
Whedon maker reference to a singular villain here
, but at this point we don't really know.
He could just as easily be talking about the leader/founder of the Masters of Evil. After all, self-centered psychopaths would need even *more* leadership to function as a group than the Avengers would. That implies a pretty capable alpha villain as the true threat, with the Masters as, essentially, extensions of his will.