Too "full o'th' milk of human kindness" to do an evil deed. Macbeth started considering killing King Duncan to gain power and become king......which will later lead him to become VERY corrupted later in the story. but it all begins in act 2
The description of a tragic hero indicates the change from nobility to his innevitable corruption in the course of a Shakespeare's play. Macbeth is considered a man of the highest honor at the beginning, however after his encounter with the "Weird Sisters" he is in the seek of his fate which implies the killing of Duncan. The right answer is too "full o'th'milk of human kindness" to do an evil deed.