In A Raisin In the Sun, which of Walter's traits contribute to the message of the play?

Of the traits the develop the most throughout the play, I
would say that Hansberry's construction of Walter as a family man is what develops with
the most vigor.  In comparison to Walter at the start of the play to how he is at the
end of it, it is evident that he becomes a stronger family man.  Walter seems to treat
his family as a source of weight and burden at the outset of the drama.  There is little
that indicates he understands his role as the head of the family.  However, his
rejection of Lindner's money and his embrace of the possibility of a better life for his
family is a critical change in how he was at the start of the play to how he is at the
end of it.  Walter sacrifices his own desires and his own self- centered notion of the
good in order to become the family man that his wife envisions and his mother hopes him
to be.  It is this critical evolution in which Hansberry's theme that one does not have
to be locked into a role by their social condition resonates the strongly.  To quote the
great Lena Horne, "It is not the load that breaks you down, it's the way you carry it." 
Walter's change throughout the play is a representation of this
idea.