Although some readers may blame Lady Macbeth more for Duncan's murder, Macbeth himself is more responsible for the murder of Duncan.
Lady Macbeth is guilty of conspiring to kill Duncan. There is no doubt about that. She flat out told her husband, Macbeth, that Duncan would not live to see another day because she and Macbeth were going to kill Duncan. "O never/Shall sun that morrow see!" Lady Macbeth is also guilty of planning the entire murder scheme, and she tells Macbeth "Leave all the rest to me."
In Act 1, Scene 7 Macbeth has convinced himself that he will not murder Duncan. Lady Macbeth then proceeds to insult and berate Macbeth. She calls him a coward and calls into question his manhood. While Macbeth is feeling down and out, Lady Macbeth lays out her plan to kill Duncan. The simplicity of it, along with her insulting "encouragement," allows Macbeth to muster the courage to kill Duncan.
While Lady Macbeth deserves a lot of the blame for Duncan's death, Macbeth is still more guilty. He is more responsible for the simple reason that he is the person who went into Duncan's room and did the actual murder. Lady Macbeth plotted. Macbeth murdered.
Macbeth is power hungry and ambitious. That's evidenced by his response to the witches' prophecy. He wants to know more about how he will be Thane of Cawdor and King. When Macbeth is awarded the Thane of Cawdor title, he immediately considers his future as king. Macbeth wonders if it will fall into his lap or if he will have to do something active. "My thought, whose murder yet is but fantastical," In Act 1, Scene 4, Macbeth is troubled when Malcolm is announced Duncan's successor.
"The Prince of Cumberland! that is a step
On which I must fall down, or else o'erleap,
For in my way it lies."
As the reader can see, Macbeth is seriously contemplating a devious act to attain the throne.
I will give Macbeth credit, he convinces himself not to murder Duncan by the time scene seven rolls around. I do understand that Lady Macbeth played a huge part in convincing Macbeth to change his mind again, but Macbeth still deserves most of the blame, because he not only thought about the benefits of murdering Duncan but also performed the physical act of murdering Duncan.