In Macbeth, which characters (besides Macbeth and Lady Macbeth) choose greed over loyalty, and what does this do to their perception of loyalty? Provide quotes for proof.

This is an interesting question. Obviously, as you've noted, the theme of greed and how this can lead to the destruction of loyalty is primarily embodied by Macbeth himself.
Early in the play, Macbeth tells Duncan that the "loyalty [he] owe[s]" to the king is so valuable that it "pays itself," stating that all he is devoted to serving Duncan and protecting his honor. Obviously, however, Macbeth's greed for power soon overtakes these feelings. Although his wife at first convinces him to kill Duncan, he becomes increasingly greedy and more disloyal, even to the point that he orchestrates the murder of his best friend, Banquo, rather than allowing Banquo to live to "produce kings" (rather than Macbeth's line taking on the throne).
Macbeth's argument for this exemplifies his greed— he says it is ridiculous that he has "murder'd" "the gracious Duncan" for the "issue" of Banquo; he suggests that he does not want to have "put rancours in the vessel of [his] peace" only for the sons of a friend to become kings (rather than his own). He does feel guilt about having murdered Duncan; he also seems to be suggesting that, having already committed the greatest sin against loyalty and duty, he may as well compound this felony with others and pursue his ambition to the bitter end.
I suppose the only other characters whose disloyalty is foregrounded in the play are those who are presented as forerunners to Macbeth very early on. In act 1, scene 2, Duncan and the Sergeant discuss the "merciless Macdonwald," a rebel who has led armies against the king and behaved like "a rebel's whore." At this juncture, Macbeth is positioned as the complete opposite to Macdonwald. Macdonwald is trying to unseat Duncan, presumably for his own gain; he has turned against the oaths he swore to the king and Macbeth kills him, winning the title "brave Macbeth."
Another person who fought with Macdonwald was the Thane of Cawdor, who "began a dismal conflict" against his king, siding with the rebel armies. This is clearly intended to prefigure Macbeth's downfall because Macbeth himself is named Thane of Cawdor as a result of this man's treachery and disloyalty. The suggestion is that "brave Macbeth" would never do the same thing as his predecessor and rebel against his king. Except, of course, he does (and worse).