How does Shakespeare present the theme of conflict in Macbeth?
There are many different possible approaches you could take to this question, but to my mind, the most interesting example of conflict in this play is the internal conflict that Macbeth himself faces after receiving the prophecy of the witches. Note how this finds its natural expression most clearly in Act I scene 7, in the soliloquy where Macbeth debates whether to act or not to act, and the various consequences of both options.
Macbeth quite clearly shows that he himself is vastly tempted to act on the prophecy. He even says that he would be willing to "jump the life to come" or risk the eternal consequences of committing regicide if he could guarantee that the crime could be carried out swiftly and without reprisals. However, when he begins to think about the consequences of such a crime, his ambition is halted as he thinks of Duncan's goodness to him and the consequences of killing somebody who is a guest in his household and somebody who is incredibly virtuous:
Besides, this Duncan
Hath borne his faculties so meek, hath been
So clear in his great office, that his virtues
Will plead like angels, trumpet-tongu'd, against
The deep damnation of his taking-off...
Thus Macbeth does show fear of killing a king who is recognised, both on earth and in heaven, as being so good. His soliloquy ends with a reflection on the way that ambition can often propel us into dangerous ground:
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'earleaps itself
And falls on th'other--
Thus we see the natural hesitation and fear within Macbeth as he struggles with his own inner conflict about what to do with the prophecy he has received. It is of course only the persuasion and cajoling of his wife (another form of conflict) that convinces or shames him into acting.