Harry was told that being a Starborn gave him power over Outsiders. What if that was just partially true, but didn't include that he has power over more than just that? What got me thinking about it was the thread about conjuring Harry is more dangerous for you, than him, and Jim saying that it isn't dangerous for Harry's Name being known as it is for others.
Another thing is that Harry seemed to defeat Mother Winter in a battle of will's I think? He doesn't have her absolute raw power, but in a battle of will, I think he won. Also his battle with Ortega, again a battle of will, and Harry was going to win. Then when Before was in Harry's mind, Harry won that battle of will as well...
In much of the dresdenverse, belief is real power. Perhaps ones will can bend reality as much as the combined belief of lots of people. Harry's Starborn gift may be an unshakable will that puts him on par with the most powerful Being's out there. He just needs to tap into it more, like when he faced Before.