The techniques that Lady Macbeth has used to manipulate her husband have been well identified and explained in the above answers. I believe the question remains of why Shakespeare chose to have her use all her persuasive powers to make Macbeth go through with a murder he did not want...
The techniques that Lady Macbeth has used to manipulate her husband have been well identified and explained in the above answers. I believe the question remains of why Shakespeare chose to have her use all her persuasive powers to make Macbeth go through with a murder he did not want to commit, a murder he deplores even while he is committing it. He tells her:
We will proceed no further in this business:
He hath honor'd me of late, and I have bought
Golden opinions from all sorts of people,
Which would be worn now in their newest gloss,
Not cast aside so soon. (1.7)
Just prior to that, in a soliloquy, he has gone over all the reasons why he should not kill Duncan. It is obviously against all his instincts and inclinations to do what his wife wants. It would seem that Shakespeare was trying his best to make Macbeth a somewhat sympathetic figure by casting the blame for the murder as much as possible on his wife. We feel that Macbeth would never have gone through with the bloody deed if his wife hadn't talked him into it. She uses "sexual blackmail" when she says:
From this time
Such I account your love.
She is suggesting that she will withhold her sexual favors if he doesn't do as she wishes. She will be be cold, indifferent, uncommunicative, moody, unapproachable.
So if Shakespeare succeeds in making us feel a little bit sympathetic for the poor man, we also despise him commensurately for being such a wimp. He is a good example of an uxorious husband, one who is dominated by his wife. By the time he faces Macduff on the battlefield in the last act, we have had enough of him. He does not have just one Aristotelian fault but a dozen. He is a murderer, a tyrant, an incompetent ruler, a bully, a psychopath, and a henpecked husband. The only thing he has in his favor is his courage. He is actually determined to fight with Fate itself, personified as an enemy warrior.
Rather than so, come, Fate, into the list,
And champion me to the utterance! (3.1)
In fact, the main conflict in the play might be described as "man against fate."