Macbeth is a hero to Scotland, and a strong person.. He is a Lord under the rule of King Duncan, and he has no reason to feel unhappy with where he is in life. It's after the meeting with the witches, that he begins to desire the throne, but he still needs Lady Macbeth to convince him to commit the murder, when he questions the consenquences and asks "If we should fail?"(I,vi,59). Lady Macbeth comes back with a quick answear "We fail', But screw your courage to the sticking-place And we'll not fail."(I,vi,60-61), what shes saying is that if he stops being afraid and pulls himself togehter they will not fail.
When Macbeth hears the prophesies of his future, he appears to disregard them, but when he is made Thane of Cawdor (as foretold by the witches), he already is thinking about killing the king when he says these words to himself "The Prince of Cumberland' That is a step On which I must fall down, or else o'erleap, For in my way it lies."(I,iv,48-50). This is why he writes to Lady Macbeth, as to prompt her for some persuasion in killing Duncan, and she later refers to the latter as his agreement of the murder when she says "Nor time nor place did then adhere, and yet you would make both"(I,vii,50-52); basically meaning that he was prepared to kill him before, and now he is too weak to go through with it.
Macbeth's true character is revealed in his thougths. Macbeth expresses these thoughts when he is thinking to himself "If chance will haveme King. Why,chance may crown me wihout my stir."(I,iii,143-144). But The thought of murdering the King, or anyone, fills him with horror, and this is why he writes to Lady Macbeth, seeking her support.After the support of Lady Macbeth and with the meeting with the witches eventually does kill his King.
After killing King Duncan , Macbeth is starting to realize what it is that he has done, and becomes suspicious and paranoid of everyone around him by putting spy's in every castle and killing those who are any treat to him what so ever. Banquo is the only other person who knows of the meeting with the witches and he would assume that it was Macbeth who killed the King. The witches also said that Banquo would beget kings but he himself would never be king after Macbeth, and so Macbeth decides that Banquo is a threat to him. To get rid of the treat with banquo he decides to kill him and his son Fleance.
At this point Macbeth is no longer the true and noble thane he once was, he is a tyrant who took the crown by force. He is evil because he killed the king with the help of his wife but becomes evil on his own because he go's off by himself in plotting the death of banquo and fleance and latter on to all of the people in the house hold of macduff. Macbeth no longer needs the push from his wife and does this on his own showing his true character. From a noble thane with graceful word such as "The service and the loyalty I owe, In doing it, pays itself"(I,iv,23-24), to words of a tyrant such as "I will not Yield, To kiss young Malcom's feet."(V,vii,28-29). Showing his disloyalty to the true and rightful king. The process form the noble thane to the tyrant is a slow one but in the end Macbeth is evil, reciving a rightful tyrants death.