Who is punished, and who is rewarded in Macbeth? What is punishment, and what is the reward?

Macbeth and Lady Macbeth are punished by their guilt.  Both of them succumb to guilt in different ways.  Macbeth slowly loses his mind, and eventually his nerve, as a result of his actions.  Lady Macbeth also goes mad, and kills herself.  Malcolm is rewarded for being brave and loyal to his kingdom, because his army defeats Macbeth’s and he becomes king. 

Macbeth’s madness started right when he killed Duncan. He said he thought he heard one of the guards say “Glamis hath murder'd sleep.”  This is the beginning of his paranoia.  He has Banquo murdered, and then sees his ghost at the banquet.  Macbeth shouts at the ghost. 

MACBETH

Thou canst not say I did it: never shake
Thy gory locks at me. (Act 3, Scene 4) 

Macbeth does not stop there though.  He has Macduff’s wife and children murdered.  When he hears the second set of prophecies from the witches, they tell him to beware Macduff.  He is so concerned about this that Macduff is able to easily confuse and upset him when the two face off in battle. 

MACDUFF

Despair thy charm;
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother's womb
Untimely ripp'd.

MACBETH

Accursed be that tongue that tells me so,
For it hath cow'd my better part of man! (Act 5, Scene 8) 

From there, Macduff beheads Macbeth and ends his reign of tyranny.  Macduff will presumably be rewarded by Malcolm, who is himself rewarded for going against Macbeth with the throne of Scotland. 

Lady Macbeth was just as much at fault as her husband.  He may have been the one who wielded the knife, but she pointed him to the king.  She was the one who encouraged him to do it.  She goaded him and called him a coward.  Yet, she felt that Duncan looked like her father and she could not kill him herself.  Later, the full weight of the murder hits her. 

LADY MACBETH

Out, damned spot! out, I say!--One: two: why,
then, 'tis time to do't.--Hell is murky!--Fie, my
lord, fie! a soldier, and afeard? What need we
fear who knows it, when none can call our power to
account?--Yet who would have thought the old man
to have had so much blood in him. (Act 5, Scene 1) 

Lady Macbeth basically screams and dies, off stage.  She killed herself because she could not handle the guilt, and she lost her mind.  She thought she saw blood on her hands that she could never wash off, because it was metaphorical!