Shakespeare showed that guilt is the worst punishment of them all and will eventually get to you and make you crack.

Macbeth shows guilt after killing the king.

After killing the king, he is very flustered by the guilt to the point that he forgot to plant the knife on the guards at first.

Macbeth shows guilt after killing Macduff.

After having Macduff kill the guilt, it makes him think he sees his ghost. All the guilt tormenting him makes him seem crazy.

Lady Macbeth shows guilt when sleep walking.

When Lady Macbeth is sleep walking she is talking about the guilt she has after having the king killed.

Shakespeare was effective in showing that guilt will get to you and torment you, because all the horrible guilt will torment you until your death.