What can you infer about Macbeth's character from his hesitation to murder the king?

Macbeth's hesitation about killing King Duncan allows us to infer that he begins the play as a relatively upright, loyal, and good man.  This inference is supported by the fact that he behaves so loyally and bravely in the battles that begin the play; the captain calls him "brave Macbeth" and graphically describes Macbeth's performance in the fight, and how he "carved out his passage" through the soldiers until he reached the traitorous Macdonwald who...

Macbeth's hesitation about killing King Duncan allows us to infer that he begins the play as a relatively upright, loyal, and good man.  This inference is supported by the fact that he behaves so loyally and bravely in the battles that begin the play; the captain calls him "brave Macbeth" and graphically describes Macbeth's performance in the fight, and how he "carved out his passage" through the soldiers until he reached the traitorous Macdonwald who he then killed in a truly spectacular and gruesome manner consistent with the man's crimes against the crown (1.2.18, 1.2.21).  Macbeth is so loyal to his king and country that Duncan rewards him with a new title, on top of the old.  It is true that Duncan has been deceived by others in regards to their goodness, but there are other reasons to believe that Macbeth is a good and loyal man.

Macbeth's wife, Lady Macbeth, believes that her husband is "too full o' th' milk of human kindness" to kill the king, and this supports the inference that he is a good man, at least to begin with (1.5.17).  Even after Macbeth and his wife have made their plans, he tells her, "We will proceed no further in this business," and he wants to cancel the plot to kill Duncan (1.7.34).  Then, once it is done, Macbeth feels so terribly guilty that not even all "great Neptune's ocean [will] wash this blood / Clean from [his] hand" (2.2.78-79).  His wife's belief that he is too compassionate to commit a murder, too kind to consider it, as well as Macbeth's own resolve not to go through with the murder, and finally his sincere guilt after having committed the murder show that he does not begin the play as the callous and cruel tyrant he later becomes.