What makes a leader effective ... an ongoing concept

Leaders are effective when people listen to them. Many writers and researchers have written a lot about leadership. Many studies identify scientifically what leadership is and what traits, behaviors, and responsibilities are "research-based" and proven to have "effects" and impacts on certain behaviors (like student achievement). What makes a leader effective is not answered or described in one post, one log, one blog, one answer. Unless the writer suggests that RELATIONSHIPS - two-way, respectful, nurturing, responsible, appropriate, mutually beneficial, and based upon common beliefs and vision - can help support an assertion that leaders are effective when they build relationships and when their leadership is built upon the foundation that people-centeredness is at least a hugely impactful starting point for effective leadership.