For me, the most impotent quality in a great leader is ''sthenia''. Sthenia is a state of normal or increased power, in comparison with standard. In simplified understanding ''sthenic person'' means a powerful personality. Sthenic person is a good at setting clear aims and achieving them. He or she has got firm conviction and their own opinion. It is absolutely not characteristic doubts and reflexion for sthenic person. It is impossible to draw him\her away. It is not good if a person is on the wrong track, so it is also impotent to have disciplined open sound mind and be able to predict consequences of actions.
The second indispensable condition is having something necessary to announce for each of us. Furthermore he\she should be a gifted person in general.
I consider a sense of humor, tact, tolerance and understanding, and dramatic talent a bit, in other words, good communication skills are necessary for a great leader. Also he\she needs readiness to repeat obvious ideas over and over again all over the world as a teacher for younger children.
Moreover, I think, it is perfect, if he\she has got a sense of fairness and high moral standards.