King Duncan's murder marks the beginning of Macbeth's downfall. Who can be held mostly responsible for this?

Although the actual murder was committed by Macbeth, many argue that he is not the person who is mostly to blame. Macbeth would have never harmed King Duncan, had it not been for the influence of the three witches. Many argue that, due to the prophecy of the three witches, which encouraged Macbeth's desire to be king, that they are the ones responsible. Others have expressed that they believe Lady Macbeth, and her part in planning for, and encouraging the murder, are mostly responsible. However, the three witches had no malicious intent, and Lady Macbeth is only an accessory. Macbeth is the individual who is mostly responsible for the murder of King Duncan.