Another one is the instructor must be able to let the students mess up. Especially letting a landing come in a little hard, sideways, etc.. Stalls that border or enter a spin, cross-country flights that go the wrong way.
In the end, as a CFI if we always make a quick correction and/or observation that immediately remedies the situation, the student really doesn't grasp the severity of thier mistakes. So I guess this ability also includes lot of patience.
My style is more "intensity" and exposure based type of training, because I feel it really drives the learning process and also show's the student all aspects of each phase of flight.