What if Macbeth had not acted upon his wife's advice?
If Macbeth's wife had not goaded him into committing the murder, it seems unlikely that he actually would have gone through with it. After he considers the myriad potential consequences of killing Duncan, he tells her, "We will proceed no further in this business" (1.7.31). He has considered the fact that he is Duncan's subject, kinsman, host, and friend; he is supposed to protect him against attackers, not wield the murder weapon himself. He has also considered the fact that simply killing Duncan will not make him king, there will be other deceptions he will have to carry out. Further, he knows that Duncan is such a great leader and a good person, and this makes it even harder for him to commit to the deed. It isn't until his wife calls him a "coward" who is "green and pale" and tells him that she will no longer think of him as a man if he refuses to go forward with their plan that he finally agrees. Therefore, had she not wounded his pride and insulted his masculinity, it seems unlikely that Macbeth would have actually committed the murder, although his marriage would likely have declined in trust and love (although, it seems to do that anyway, even when he takes her advice).