You will see examples throughout the book: when Banquo stays with Macbeth hiding his suspicion while Macduff rides away telling others of the murder, when the ghost of Banquo haunts Macbeth while Macduff refuses to attend the feast at all and finally throughout the play we see the prophecy of Banquos sons driving Macbeth mad; Macduff using Macbeths reliance on the witches as a weakness to attack and kill him. Banquos suspicion causes Macbeth to worry, not knowing that Macduff had left with his own suspicions.
We see the different approaches of the two characters, Banquo hiding his thoughts and sticking close instead of openly discussing his thoughts like Macduff. Banquo has clued in on the connection between the wyrd sisters prophecy and the murder of Duncan, questioning Macbeths morality ¦ King, Cawdor, Glamis, all¦ I fear / thou playedst most foully for it (3. 1. 1-3). Banquo contains his distrust, watching Macduff from the shadows as he leaves the clearer target. Macduff was the first to find the body of Duncan and does not worry about his own safety, discussing his knowledge with Ross and the Old Man.
We see his wording in act 2 scene 4 as doubtful, not believing Macbeths reasoning for killing the guards in Duncans room. Macbeth still does not see the works of Macduff, who does not attend his crowing ceremony, and is strictly focused on Banquo. He admits to having fears in Banquo [which] stick deep and plans on disposing of him (3. 1. 50-51). Macbeth knows he can no longer trust his once best friend as paranoia and insanity begin to set in. This distraction is the reason Macduff is given leeway to spread his distrusts through the group of secondary characters.
In effort, Macbeth has made up his mind to continue onwards with fulfilling the prophecy, a decision that will literally haunt him greatly. The ghost of Banquo terrorizes Macbeth at his banquet, making him act a fool in front of all the thanes. Macduff denies Macbeth publicly by not attending, thus upsetting him greatly. Banquos role is further shown to be private or solely concentrated to Macbeths knowledge, giving him an insane outer appearance. Macbeths mentality only feeds the fire in Macduff as he gains more and more reassurance from the onslaught of murders.
We even see his own wife accuse him of displac[ing] the mirth, break[ing] the good meeting / with most admird disorder (3. 4. 109-110). Banquo has terrified Macbeth, making his cheeks ¦blanchd with fear (3. 4. 116) sending him looking for an outlet; the absence of Macduff. He admits to having a servant fed (3. 4. 132) in all of his thanes houses and knows that Macduff has denied the invitation on purpose. He takes this as an extreme insult, planning to kill Macduffs family as a punishment. This section has shown Macbeth as very weak and incapable of rational thought processes, taking the absence of a thane as the reason to kill.
The fate of Macduffs family is set in stone, much like Banquos, yet it will not grant him anymore safety and will in fact lead him searching for security. Macbeth goes back to the wyrd sisters to gain some more insight on the prophecy. He goes out of desperation, hoping that his fate still holds true to what he has been told and the throne will be forever in his family. Banquos sons have forced the hand of Macbeth, pleading the witches not for the truth, but to hear what he wants. The haunting of Banquos children has led to the murder of Macduffs.
Action caused by children has connected Banquo and Macduff, as the newly deceased and the future kings will not let Macbeth free. Macbeth takes the witches new prophecy not for what it is, but as what he wants it to be. His head has been inflated, and no longer worrying about the thrones next owner. Macbeth is at a point where he has nothing to lose and after his wife dies, he is at wits end. Macbeth knows the fate of his kingdom, and will die with harness on [his] back (5. 5. 51). He had thought he was invincible, Banquo had been a nagging recurrence and had punished him mentally.
Exhausted, he chose to face and die by the army and Macduff, his true match. Through different ways, Macduff and Banquo were able to break Macbeth both mentally and physically, bringing his reign of terror to an end. Banquo, through suspicion was able to distract Macbeth, his ghost returning, constantly reminding him of his deeds. Macduff, meanwhile, gathered his thoughts and fought Macbeth every step of the way. Using rational methods, he was able to take down a very irrational man. Banquo had written the book all along, all he had to do was wait for Macduff to publish it.