The downfall of Macbeth was a great tragedy. He knew it was not right to kill the king, but he felt he had no other choice. He was trapped into doing wrong. Lady Macbeth gave him the evil ideas throughout the play. She was his driving force. Without her, Macbeth wouldnt have done what he did. Therefore, Lady Macbeth is as much of a main character as Macbeth is.
Macbeth says, Stars, hide your fires; Let not light see my black and deep desires(1.4.57-58). Here he is expressing that while he does want to become king and may have a few evil thoughts of how to achieve that dream, he does not plan to act on them. It is not until Lady Macbeth talks to him that he is a bit more convinced. Speaking of King Duncan, she states, O, never shall sun that morrow see! (1.5.71-72), basically ordering Macbeth to murder him in their own house. Lady Macbeth is obviously the evil one. That is apparent when she gets Macbeths letter and responds by saying, Yet do I fear thy nature. It is too full of the milk of human kindness(1.5.16-17). This shows that she knows Macbeth will not murder Duncan on his own. She takes matters into her own hands and decides to convince him.
Macbeth opens scene seven by giving a long list of reasons not to kill King Duncan. He is his ruler and kinsman, his guest, and a virtuous king. With this list of reasons Macbeth slowly convinces himself not to commit the murder. He then informs Lady Macbeth of his decision to proceed no further in this business(1.7.34). Lady Macbeth challenges that and calls him a coward, not a man. She accuses him of going back on his sworn word to her, and with very violent language declares that she would dash out the brains of her own baby, had she promised to as Macbeth had promised to kill Duncan. She then assures Macbeth that failure is impossible, at which point Macbeth is convinced once again to kill the king. Macbeth had resolved not to kill the king after much thinking about it, but Lady Macbeth persuaded him to do it.
Not only did Lady Macbeth convince her husband to murder King Duncan, but she also made the arrangements to make it possible. At the beginning of Act two, scene two Lady Macbeth informs us that the guards are thoroughly intoxicated. She goes on to say, I laid their daggers ready; He could not miss em(2.2.15-16). Lady Macbeth made all the arrangements necessary for the murder of King Duncan, so that all Macbeth had to do was perform the act.
In conclusion, Lady Macbeth convinced Macbeth to murder Duncan, convinced him again when he was unsure, and made all the proper arrangements which is why Lady Macbeth is as much of a main character of the play as Macbeth himself is. Macbeth did not want to murder Duncan in the first place until his wife talked him into it. Then, when he changed his mind, Lady Macbeth taunted him until he agreed once again to murder the king. Finally, Lady Macbeth made sure that everything was set up for the murder. On the surface it would appear that Macbeth was responsible for the murder since he committed the crime, but when more is read into it, it becomes clear that Lady Macbeth was more responsible.