This is an often asked interview question. Below are some tips and sample answer to this question.
Focus on two words: leadership and vision.
Here is a sample of how to respond: "The key quality in a successful manager should be leadership--the ability to be the visionary for the people who are working under them. The person who can set the course and direction for subordinates. The highest calling of a true leader is inspiring others to reach the highest of their abilities. I'd like to tell you about a person whom I consider to be a true leader..."
Then give an example of someone who has touched your life and how their impact has helped in your personal development.