Also known as the Comte de Rochefort. D’Artagnan first encounters him at Meung; D’Artagnan was visibly upset when Rochefort insulted his janky yellow horse.
Although he too is an agent of the Cardinal, we don’t see much of Rochefort throughout the novel. He functions as a vague ominous presence who D’Artagnan considers his mortal enemy. At the end of the novel, however, D’Artagnan gets his dearest wish and the two men have multiple duels, each of which D’Artagnan wins. They finally agree to fight no more, and the novel ends with the two of them on their way to friendship. Awww.