"Macbeth" is one of Shakespeare's most well-known tragedies. The character Macbeth is an ostensibly loyal servant of the king who goes on to kill the king and usurp the throne. With that one decision, Macbeth begins his descent. His course of action costs him his wife and, ultimately, his own life. Though Macbeth commits many unspeakable acts throughout the play, Shakespeare makes him seem sympathetic by establishing some evidence of good character at the start of the play and showing his struggle and regret over some of those bad decisions.
Before the Fall
Macbeth is first introduced as a noble and respectable man. He is presented as having fought valiantly for the king and being a loyal subject. He is referred to as "brave Macbeth -- well he deserves that name" and "valiant cousin! worthy gentlemen!" He is characterized as a brave man who fights with dignity. By presenting Macbeth as an honorable man at the start, Shakespeare encourages the audience to feel warmly toward him, which inspires their pity and sympathy when he falls.
It is not Macbeth's idea to kill Duncan, the king. After the witches tempt Macbeth by giving him a prophesy that he will be king, Lady Macbeth encourages Macbeth to make it come true by murdering the king. Lady Macbeth acknowledges that Macbeth "is too full o' the milk of human kindness" to do such an act himself, so she pushes him into the plan. Macbeth recognizes the evil of the action, but he is not so "full o' the milk of human kindness" that he spares the life of his cousin the king. Knowing that Macbeth was led to the idea and fell to temptation -- even the temptation of his own ambition -- helps the audience to sympathize with him.
Moment of Hesitation
After Macbeth agrees to kill the king, he experiences a moment of hesitation and argues to Lady Macbeth why it's wrong. Lady Macbeth taunts him by challenging his manhood and again appealing to his ambition, convincing him to act. Seeing Macbeth struggle with the choice helps the audience to sympathize with him. Though Macbeth is ultimately responsible for his own choices, he is influenced by many forces, including Lady Macbeth's manipulation and his own character flaws.
Macbeth may finally agree to kill the king, but he is tormented by the decision for the remainder of his life. He has nightmares about what he's done, and he begins to hear voices at night. He eats very little, and he feels that he is so evil that he cannot say "amen." By showing his torment, Shakespeare makes it easier for the audience to sympathize with him and recognize that he has goodness in him, even if he has flaws that eventually lead to his downfall.