If I were to pick the one characteristic that is essential to leadership it would be credibility.
Credibility can rest on the actual ability to lead, the perceived ability to lead, and the integrity that causes others to place their trust in the leader. The integrity involves a certain reliability that permits the followers to know that the leader will, within reasonable boundaries, be predictable. A leader who is frequently unpredictable will soon lose followers and resemble the man who jumped on a horse and rode off in all directions.
A major reason why so many executives, managers, and supervisors fail in their leadership responsibilities is they have, in either a dramatic event or a series of damaging actions, lost credibility. How is credibility lost? The ways are too numerous to list but the usual suspects are insensitivity to others, failing to keep commitments, and failing to produce. One trucking executive put it well: "People don't give you their trust; they only lend it to you."