I would offer the following as essential qualities of spiritual leaders. He or she must love others enough to tell them when they are wrong and love themselves enough to admit when they are in the wrong. Most of the spiritual leaders I know are more than ready and willing to tell me what my shortcomings are but are virtually silent about their love for me, my family, or my churches. People listened to Jesus preach and teach for hours on end because they knew He loved them. They knew that because He healed their sick, raised their dead, and fed them when they were faint from hunger.
Love is the most important qualification for spiritual leaders.
A second equally important characteristic of a spiritual leader is faithfulness. Most of the prophets who were faithful to the message God gave them were not wildly successful in terms of changing minds. I seriously doubt Jeremiah would have received an enviable appointment under today's system. People who are faithful to God's calling in their lives are often not very good players in the game and pay for it. Lastly, spiritual leaders must surely be holy.