Shakespeare, in a series of soliloquies in the first two acts, portrays Macbeth as vacillating and torn by conflict over whether to kill Duncan. His ambition pushes him to commit the murder, but his sense of right and wrong is always there, and in fact, by the end of his soliloquy at the end of the first act, he says that he has decided not to go through with the act. His wife, on the other hand, emerges as a completely unsympathetic character. Her soliloquy after reading Macbeth's letter in Act I, Scene 5 is one of Shakespeare's most chilling:
Come, you spirits
That tend on mortal thoughts, unsex me here
And fill me, from the crown to the toe, top-full
Of direst cruelty! ...Come to my woman's breasts,
And take my milk for gall, you murdering ministers,
Wherever in your sightless substances
You wait on nature's mischief!
Macbeth's soliloquy in Act I, Scene 7, mentioned above, portrays him as still having some sense of right and wrong, though he could also be construed as weak and vacillating:
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on the other—
It is a stretch to call Macbeth a sympathetic character at this point, but at least he seems human. His wife, on the other hand, is brutal in her attempt to challenge her husband's masculinity and his integrity by claiming that she would do anything rather than go back on his decision to kill Duncan and seize his destiny:
I have given suck, and know
How tender ’tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this.
So Lady Macbeth is portrayed as a thoroughly unsympathetic character early in the play. Her husband, however, is seen as gradually descending into evil, and he has lost any sense of right and wrong by late in the play.