How we cite our quotes:
BANQUO Thou hast it now: King, Cawdor, Glamis, all, As the weird women promised, and I fear Thou play'dst most foully for't; yet it was said It should not stand in thy posterity, But that myself should be the root and father Of many kings. If there come truth from them (As upon thee, Macbeth, their speeches shine) Why, by the verities on thee made good, May they not be my oracles as well And set me up in hope? But hush, no more. (3.1.1)
Sure, Banquo didn't murder anyone for self gain, but he may not be as honorable as he seems. He suspects Macbeth of foul play, but does he tell anyone? No. In fact, he tells himself to "hush"—maybe because he's a little too excited about being the "root and father/ Of many kings."
MACBETH […] For mine own good All causes shall give way. I am in blood Stepp'd in so far that, should I wade no more, Returning were as tedious as go o'er. (3.4.24)
In case we still had some lingering doubts, Macbeth clears that up for us: he's doing all this "For mine own good." Great. We'll be sure not to ask him for any favors, then.
MACDUFF […] Either thou, Macbeth, Or else my sword, with an unbatter'd edge, I sheathe again undeeded. There thou shouldst be; By this great clatter, one of greatest note Seems bruited. Let me find him, Fortune! And more I beg not. (5.8.1)
This is how to do ambition right: Macduff wants to avenge his family and his king, but he doesn’t seek power for himself. He doesn't want to rule fortune; he's content to be fortune's tool. Clearly, he's going to be the one to take down the boss.