The following extract from Act One, Scene Two, clearly indicates that Macbeth is courageous and enters into battle undaunted:
For brave Macbeth--well he deserves that name--
Disdaining fortune, with his brandish'd steel,
Which smoked with bloody execution,
Like valour's minion carved out his passage
Till he faced the slave;
Which ne'er shook hands, nor bade farewell to him,
Till he unseam'd him from the nave to the chaps,
And fix'd his head upon our battlements.
The above description about Macbeth's valour comes from a report to King Duncan, provided by an injured sergeant who had just returned from the battlefield and had witnessed Macbeth in action. He emphasises Macbeth's fearlessness and mentions that Macbeth had ignored destiny. Macbeth was swinging his sword which was steaming from the hot blood of his vanquished enemies. As if he were a disciple of Courage, Macbeth carved out a path through the opposition until he faced MacDonwald, who he then cut in two, from his navel to his jaw. He then beheaded him and placed his severed head upon the castle wall.
Macbeth's villainy is shown in scene three. After being informed by Ross that the king had bestowed upon him the title Thane of Cawdor, Macbeth, in an aside, clearly expresses his intention of achieving Duncan's title:
[Aside] Glamis, and thane of Cawdor!
The greatest is behind.
Macbeth here suggests that the greatest hurdle to his ambition has now been crossed. All that stands in his way is the king himself. He later expresses the following thought:
[Aside] Two truths are told,
As happy prologues to the swelling act
Macbeth is saying that the truths divulged by Ross, and predicted by the witches are pleasing indicators that he would be king (the swelling act). This indicates that Macbeth had already been plotting about getting rid of Duncan. This is further supported by a later aside in which he confirms the horrible reality of his scheming:
Cannot be ill, cannot be good: if ill,
Why hath it given me earnest of success,
Commencing in a truth? I am thane of Cawdor:
If good, why do I yield to that suggestion
Whose horrid image doth unfix my hair
And make my seated heart knock at my ribs,
Against the use of nature? Present fears
Are less than horrible imaginings:
My thought, whose murder yet is but fantastical,
Shakes so my single state of man that function
Is smother'd in surmise, and nothing is
But what is not.
Macbeth clearly expresses what his intentions are in this extract. He refers to the witches' predictions, stating that they cannot be good nor can they be bad either, for why would they have made the promise if it were not to turn out so well - he is now Thane of Cawdor as they predicted. He questions the idea of why he should now be so fearful when it is his destiny. It is against his nature to be afraid. He dismisses his fear as being an imagination run wild and accedes that it is only the thought about having to commit a foul act (killing his king) that shakes him up and makes him wonder too much, thus making his lose his composure. Nothing, however, is certain.
The extract is a profound indication that Macbeth has already thought about usurping the throne in some way or another, thus making him a villain.