One of the ironies in the play is that Lady Macbeth convinced her husband to kill Duncan, and then committed suicide because of the guilt.
Irony is when the opposite of what you expect happens.
Lady Macbeth is a real go-getter. She wants to get ahead in life, and the only way to do that is to help her husband get ahead. Unfortunately, he does not seem to have much ambition. When Macbeth tells her that three witches told him that he was going to be king, she latches on to that idea and convinces him to take it even if it isn’t given to him.
Macbeth is not convinced that killing the king and taking his spot is the best idea. After all, the king has named his son Malcolm as successor, and he has another son too. He tries to tell his wife it’s not a good idea for several reasons, but she disagrees.
If we should fail?
But screw your courage to the sticking-place,
And we'll not fail. (Act 1, Scene 7)
The irony is that while she is able to tell him every little detail of how to carry out the murder, she is not able to commit it herself. She even chides her husband for taking the murder weapon with him, getting her hands bloody when she returns it. As her husband becomes more and more delusional, Lady Macbeth beats him to the punch by completely losing it.
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? ... (Act 5, Scene 1)
In her famous sleepwalking scene, Lady Macbeth struggles with her guilt in a literal way. She imagines spots of blood on her hands that she can’t wash off. These illusory spots are the vestiges of the real spots of blood she got on her hands when handling the murder weapon, but they represent her role in the murder.