The adjectives I would use here are ambitious, obsequious, paranoid and evil. The most important adjective here is most certainly the first one! Why? Because it is Macbeth's ambition that makes him one of Shakespeare's most notable tragic heroes. Macbeth admits this himself when he says:
I have no spur / To prick the sides of my intent, but only / Vaulting ambition, which o'erleaps itself / And falls on th' other--
It is this ambition, in addition to his mindless following of his wife's advice that cause him to murder. This leads me to the second adjective: obsequious. Macbeth does nothing if he doesn't follow his wife's lead. In fact, many critics think that Lady Macbeth is the true genius behind Macbeth's evil! What is the first thing Macbeth does when he hears about the prediction? Writes his wife a letter to see what she thinks! She then says,
Come, you spirits / That tend on mortal thoughts, unsex me here, / And fill me, from the crown to the toe, top-full / Of direst cruelty?"
Why? To convince her husband! ... And she does a heck of a good job, too! Little Macbeth follows along, not unlike a little puppy dog and lets his evil wife lead him forth into evil.
Now to deal with the fact that Macbeth is paranoid. It is the evil in the witches' predictions that make him thus! Everything from finding the ghost of Banquo sitting at the banquet, ... to Macbeth's own order of murder. And can there be anything more indicative of paranoia than looking around frantically for walking trees? Of course, he's worried about those Birnam Woods coming to Dunsinane. In my own opinion, I think that Macbeth is more paranoid about the witches' predictions coming true than he is protective of his own kingship.
Finally, we can't neglect the fact that Macbeth is evil, ... or perhaps I should say that he turns evil in the context of the play. Thanks a lot, Lady Macbeth! Simple ambition turns sour when that ambition turns to murder. Macbeth murders on his own, ... and he hires others to murder for him. There is no doubt that an evil person only would commit this type of crime to raise his own station! No wonder the witches spend lots of time laughing at Macbeth!
As a warrior, Macbeth is a skillful soldier. For Macbeth's competence, King Duncan showers him with praise and honors. For his bravery, King Duncan presents Macbeth with his new title, Thane of Cawdor.
At one point, Macbeth is indecisive. He changes his mind about murdering King Duncan. He insists that he and Lady Macbeth will proceed no further in the murdering of King Duncan:
We will proceed no further in this business.
He has recently honored me, and I now have the
Golden opinions from all sorts of people,
Which I want to enjoy for a bit longer, and
Not cast them aside so soon.
Later, Macbeth is dangerous. As a man with mixed emotions, Macbeth is easily influenced by Lady Macbeth. She is so filled with desire to become queen until she plans the murder of King Duncan. Macbeth kills Duncan as he sleeps. Then he kills the guards who were to protect the King. Murdering innocent victims is becoming too easy for Macbeth.
As a murderer, Macbeth is evil. One murder leads to the next. Macbeth has his friend Banquo murdered. Then he has Macduff's family murdered. He has Lady Macduff and her children murdered.
Macbeth is quilty. He begins to show signs of guilt. Macbeth sees Banquo's ghost. Likewise, he cannot sleep. He is plagued with a guilty conscience. He hears voices crying sleep no more:
Still it cried, "Sleep no more!" to all the house.
"Glamis has murdered sleep, and therefore Cawdor
Shall sleep no more. Macbeth shall sleep no more!"
Clearly, Macbeth is filled with guilt until he shall never find rest again.