Mandela's commitment to a world in which apartheid does not exist is probably one of his strongest attributes as a leader.  Mandela never wavered.  Despite intense pressure to do so and intense intimidation to acquiesce, he simply became more pronounced in his opposition to apartheid.  Torture, maximum security facilities, as well as elements that would make regular people recant all were used against Mandela.  All of these measures failed.  Mandela did not cut any secret deals.  He did not seek an easier path.  He provided leadership against an authority structure that was relentless in seeking to oppress millions.  This is his greatest attribute.  When the idea of leadership is conceived, the ability to stand up for one's beliefs despite intense pressure has to be seen as a part of the equation.  Mandela represents this in how he never relented in his desire for a world where the structure of apartheid is absent.  Providing this leadership for so many that were under the heel of apartheid is where his attributes are on greatest display.  In a world that stunted the ability to imagine of another alternative, Mandela's leadership that showed commitment, strength, and an unwillingness to compromise on values are his greatest attributes.