Fagin and Macbeth are both opportunists who had little moral character of their own, but were manipulated by people who were even more greedy and evil.
Although both Fagin and Macbeth were bad people, they were essentially not the worst people in either of their stories. Dickens and Shakespeare both had similar messages. Fagin and Macbeth were both puppets, and while they were both opportunistic, slimy, whiny, rotten people, they both had truly evil, despicable, skin-crawlingly horrible people pulling their strings!
In Fagin’s case, the puppet master was Sikes, the all-around criminal. Sikes was an abusive, disgusting, and genuine bad guy. Fagin was just a mewling pig compared to him. Fagin was the fence (the one who sells the goods that are stolen), but Bill Sikes was the one who broke into the houses to do the stealing. Fagin was just as afraid of Sikes as anyone else.
'Hush! hush! Mr. Sikes,' said the Jew, trembling; 'don't speak so loud!' …
'Well, well, then--Bill Sikes,' said the Jew, with abject humility. 'You seem out of humour, Bill.' (Ch. 13)
Sikes’s plans regarding Oliver are essentially carried out. Although Fagin is no rose, he does not want to go against Bill. He will argue with him, but he is definitely afraid of him. Fagin is an old man, and a coward. Bill is strong and resourceful, and Fagin knows he has the upper hand. Fagin goes along with what he says. He agrees to a plan to kidnap Oliver, an innocent boy, and frame him. Fagin knows this will destroy the boy and lead him to a life of crime. But he has basically no spine or moral compass. He goes along with it because he doesn’t care, and he doesn’t have the will to go against Sikes.
Macbeth is a war hero. He is a brave soldier whose exploits are praised to the king, and we expect him to be a strong and noble man. This is until we see him with his wife. We soon learn that when it comes to Macbeth, the women are in charge. First, the witches manipulate him into thinking he is about to be king. Then, when the king hands that honor off to his son (the person most likely to get it, after all), we see Macbeth for the whiny and easily manipulated little man that he is. Are you beginning to see the similarities with Fagin? Macbeth’s wife is just as abusive and manipulative as Sikes was. You might even say she is downright cruel to her browbeaten husband, questioning his masculinity.
He will again be well: if much you note him
You shall offend him and extend his passion:
Feed, and regard him not. Are you a man? (Act 3, Scene 4)
Lady Macbeth, who pounced on the idea that Macbeth would be king, gives him specific instructions. When he warbles, not sure that the idea is right, she comes up with a specific step by step plan and makes sure that he follows it. She scolds him if he does not follow the plan to the letter (he doesn’t leave the daggers behind, and she gets on him about it like a nagging wife). Macbeth basically goes from a brave soldier with some ambition to a serial killer in a short period of time, because a few witches and his wife push him into it.
Unlike Fagin, who remained fairly harmless other than keeping his gang of boys employed in light criminal activity, Macbeth turned into a real killer through his wife and the witches’ intervention. After killing Duncan he killed Banquo, Macduff’s family, and then started an all-out war.
Great Dunsinane he strongly fortifies:
Some say he's mad; others that lesser hate him
Do call it valiant fury: (Act 5, Scene 2)
He was truly despicable. On the other hand, you could argue that it was bad enough that Fagin was responsible for turning groups of boys to a life of crime for generation after generation. He also treats his boys very badly. At one point he beats Oliver with a club. Sikes even comments about how Fagin treats them, and he is abusive to both his girlfriend and his dog!
What are you up to? Ill-treating the boys, you covetous, avaricious, in-sa-ti-a-ble old fence?' said the man, seating himself deliberately. 'I wonder they don't murder you! I would if I was them. If I'd been your 'prentice… (Ch. 13)
Would these two men not have become kidnappers and murderers on their own? Doubtful (they don’t have the brains or energy). Were they men of despicable character on their own? Absolutely. They probably would have gone on committing their own petty acts of small crimes insolence, or in Macbeth’s case, letting the murderess impulses out in the societally appropriate way through war. However, the influences of the real villains turned them into truly terrible people, and then they continued to corrupt from there.