One of the epithets for Buddhahood is "The Great Fearlessness".
The point being that at the end of Path there is no fear, but obviously at the beginning there is. Since fear is such an strong operating principal in the spiritually immature, the enlightened use it to move the unawareness of the student towards awareness. It is seen as the thing that will motivate the immature to take action. Later in the teachings, both historically and personally, that emphasis on fear changes towards love, because for the spiritually mature love then becomes the effective operating principal. Ultimately at the end of the Path fear completely disappears and all that is left is love. (Or so I've heard.)
There is a tradition of making a distinction between two different perspectives on the nature of emptiness: one is when emptiness is presented within a philosophical analysis of the ultimate reality of things, in which case it ought to be understood in terms of a non-affirming negative phenomena. On the other hand, when it is discussed from the point of view of experience, it should be understood more in terms of an affirming negation.