Although you have not included the excerpt, it is possible to answer this question. The lines in which it is implied that Macbeth considered Duncan a good man are these: <em>"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-tongued, against / The deep... of his taking-off." </em>
Macbeth is here praising Duncan's humility (<em>meek</em>) and purity (<em>clear</em>) as a ruler (<em>faculties</em> can be understood as royal duties), and he is sure that, when he dies (<em>take off</em>), his virtues will shout to the four winds the injustice of his death. In this wonderful and powerful soliloquy (a speech that Macbeth is speaking to himself), the loyal yet ambitious subject is struggling between his duty, his conscience, and his fear on the one hand, and his ruthless ambition, on the other hand.
