Effective leadership has no one set definition. To me an effective leader is someone who confidently guides others toward a common goal while effectively managing the characteristics of the group. The two qualities I find most important in an effective leader would be good communication and emotional intelligence. These two qualities could greatly assist an effective leader in building a strong team even when skill and talent are not amply available.
Good communication gives the leader the ability to clearly explain their vision to the team. It helps them to be able to detail the strategies to be used in achieving this vision or goal. If you cannot illustrate to your team the results you want it will be difficult to achieve them. Therefore, without the ability to communicate clearly with your team you will never be able to successful guide them, motivate them, or instruct them effectively to achieve the results, vision, or goals you desire as a leader.
Emotional intelligence gives the leader the ability to increase their influence over their team through the acceptance of what they are saying. They do this by establishing an emotional bond or connection with them that builds trust and understanding. Emotional intelligence is very important when it comes to seamless communications, conflict resolution, managing emotions effectively, and a better social awareness of the team and its members. Leaders have the ability to better control their own emotions preventing their own negative feelings from impacting their decision-making abilities. This reduces knee-jerk reactions and shoddy decision making. Leaders with great emotional intelligence have a great compacity to understand the feelings and emotions of the members of their team. This ability assists in better conflict resolution, being able to understand concerns from the point of view of the team member, and orchestrate resolutions that are for the betterment of the team overall versus just the primary parties involved.
There are so many important qualities to being an effective leader. For me, if you can not understand the people you are working with or how to properly explain ideas and concepts to them then you will not be a very effective leader. Clear communication and deeper understanding of people and their needs is necessary in all areas of your life not just in leadership roles. This makes these two qualities the ones I would consider the most important overall other qualities.