Macbeth has several plot holes.
- Lady Macbeth, in Act I Scene 6, when she's insulting her husband's manhood because he doesn't want to kill Duncan, she says, "I have given suck, and know / How tender 'tis to love the babe that milks me...," yet Macduff says, in Act IV, Scene 4, that Macbeth has no children. (I suppose it's possible that Macbeth's children died in infancy, but we have no direct indication of that.)
- Macbeth hears all the prophesies, including "Beware Macduff!" "no man born of woman can harm you," and "you'll be safe until Birnam Wood comes to Dunsinane," but even after he sees the final "impossible" prediction come true--which clearly indicates that the witches tell the truth, but he's interpreting it wrong, he still considers himself invincible since he cannot be killed by any man "of woman born."
- In Act 2 Scene 3, Macduff discovers the murdered Duncan along with his slaughtered guards, and Macbeth feigns ignorance and surprise; however, when Lennox says that it seems Duncan's guards killed him but were dead, Macbeth says, "Oh, yet I do repent me of my fury, / That I did kill them." If he were ignorant of Duncan's murder, he would never have had the chance.
- If Macbeth truly believed that the witches had spoken the (unchangeable) fates of himself and Banquo, there would be no point in trying to kill Banquo and Fleance. You can't change fate. But he believes it enough to try to change it (thinking about this problem should give you a brain trip.)
- This isn't really a plot hole, but it doesn't make sense that Macbeth--who was urged to murder by his trusted (conniving) wife, would not tell her about his plans to murder Banquo and Fleance. She would, no doubt, have had his back on that one, too, and he'd have had someone to confide in and help him through the mental torture he knew would follow (considering how distraught he was after Duncan's murder).
- Considering how Duncan and his guards were murdered, the murderers would have had blood all over them. Macbeth and Lady Macbeth had no time to clean up and change after the deed before Macduff discovered the body. By the same token, Malcolm and Donalbain would have clearly been innocent.