In your opinion, what is that one trait that makes someone a good leader?

i think there are more then one trait SIDRAH ...Quality of leading from front and listening to others, handling conflicts , earning respect, providing solutions, bring every one together to succeed towards one goal.

Altruism

Honesty

Honor                                                  .

Not one. I will recommend the following 7.

... inspire action.

Try to paint a vision of the future that inspires your people to do whatever it takes to get there. The best leaders also clear away the organizational roadblocks that constrain employees’ natural creativity and initiative, unleashing a tremendous amount of energy in the process.

... be optimistic.

We all want to work with and for people who lift us up into the clouds instead of dragging us down into the mud. Make sure to seek out the positives in your people, helping them overcome their own feelings of self-doubt and spreading optimism throughout your organization.

... have integrity.

Research shows that the top thing that employees want from their leaders is integrity. Be honest, fair, candid and forthright, and treat everyone in the same way that you yourself would want to be treated.

... support and facilitate your team.

For people to do their very best work, they need an organizational environment that supports them by making it safe to take risks, to tell the truth, and to speak up ... without being punished for doing so. Support your employees by creating this kind of environment, and it will facilitate their progress toward attaining your organization’s goals.

... have confidence.

Highly effective leaders know deep down inside that they and their team can accomplish anything they set their minds to. Failure is not an option. Tentative leaders make for tentative employees. If you’re confident, your people will be too.

... communicate.

In any organization, knowledge is power, and great leaders ensure that every employee, from the very top to the very bottom of the org chart, is provided with complete and up-to-date information about the organization’s goals, performance, successes and failures. To achieve this level of connection, you should also provide ample channels for two-way communication between employees and managers, actively soliciting their ideas for improvement and rewarding employees for submitting them.

... be decisive.

One of the most basic duties of any leader is to make decisions. Highly effective leaders aren’t afraid to be decisive and to make tough calls quickly when circumstances require it. Once you have all the information you need to make an informed decision, then don’t hesitate--make it. And once you make a decision, then stick with it unless there is a particularly compelling reason for you to change it.

The one leadership quality I'd choose is the ability to inspire and motivate his/her team based on their individual level of competence and commitment. 

I believe that honesty is the most important feature

There are many traits makes a good leader such as openness,decisiveness, consciousnessand Honesty . I think that last one is the most important because Honest leaders inspire not just through words but through actions. They're the kind of leaders who build their teams from the ground up. They understand that effective leadership is built on trust, and that honesty in leadership generates a stronger team dynamic. Honest interactions with employees build the kind of relationships that make success in the workplace attainable for the entire team not just the boss.

Inspiration

Inspiring leader is someone who communicates clearly, concisely, and often, and by doing so motivates everyone to give his or her best all the time. They challenge their people by setting high but attainable standards and expectations, and then giving them the support, tools, training, and latitude to pursue those goals and become the best employees they can possibly be.

I agree with experts answers, thanks for the invitation. .