A great leader knows his team's strengths and weaknesses. He knows what they can collectively achieve together, and he can see what they are capable of—even when they cannot. He can also see where they are likely to face challenges.
A great leader also knows each member of her team as individuals. She knows their strengths, and she knows what motivates and drives each one. She can also see their blind spots—the areas where they need help, coaching and improvement. This knowledge allows her to communicate effectively with each member of her team.
Great leaders spend time with their teams and acquire knowledge of their strengths and weaknesses collectively and as individuals. More important, though, truly great leaders know their own strengths and weaknesses. They know the areas in which they do exceptionally good work and those in which they don't.
Truly great leaders know when they have the vision, passion and message and when they need to hold others accountable for execution. Truly great leaders know that the inclination toward growth is both an asset and a liability and that they sometimes underestimate the amount of work it takes to realize their ambitions.