Give a description about Ali that "paints a picture" of his character.

I think that part of Ali's character is the reflection of
how there can be transcendent values in a world of contingency.  Ali might be poor and
might be someone that does not possess power in the conventional sense of the word. 
However, he does have dignity.  It is this that allows him to be loyal as a servant to
Baba and Amir, but also is one that prevents him from living with shame.  It is
interesting to see how in a crumbling social fabric of Afghanistan, Ali represents an
aspect of permanence. He might be a member of the Hazzara, a perceived "lower group." 
While there is continue entropy around him and a seduction to embrace the ease of the
moment, Ali stands as tall as he can and would rather experience life as someone without
a home than one where his son is thought of as a thief, something he knows is not true. 
Ali is one who might be a servant, but is one who does not serve.  His character is
important because in a world of transitory and contingent values, oftentimes there is a
lack of stature present.  The very fact that Afghanistan devolves into such a condition
where someone like Assef could actually hold power is indicative of this.  Yet, Ali
represents that there can be permanence and dignity even in the most disparaging of
conditions.  Even before anyone else, Ali's characteristic dignity might prove that
there can be a chance to "be good again" when so much around us is
not.