How we cite our quotes: (Part.Letter.Paragraph)
Quote #4
[Prévan] is, at any rate, the only man today whom I should not care to have cross my path; and whatever you do in your own interest, you would be rendering me a great service if, in passing, you were to bring down a little ridicule upon him. (2.70.5)
Prévan's sin, according to Valmont, is being popular with women and therefore, a rival to Valmont. For Valmont, life is a zero-sum game. Someone else's win is his loss. So Prévan has to be taken down, and he knows that the Marquise would love revenge against Prévan's boast about seducing her.
Quote #5
My plan […] is to show her virtue breathing its last in long-protracted agonies […] And could I take any lesser revenge upon a haughty woman who, it seems, is ashamed to admit she is in love? (2.70.7)
Valmont is truly diabolical. He seeks to corrupt the most virtuous woman he knows, destroying not only her marriage and reputation, but her very soul. And what's her crime? Not admitting she's in love with him. That reprisal seems a bit…disproportional. Actually, Valmont's seduction of Madame de Tourvel isn't revenge like some of the other schemes, because she's never wronged him. It's completely unprovoked. It's almost as if her very existence is an affront to him—a virtuous woman who isn't interested in being his lover. Imagine that.
Quote #6
After all, it is not upon me but upon your faithless mistresses that you must take revenge. I can provide the opportunity. (2.79.20)
Prévan is slick. He wrongs three men by seducing their lovers, and then manipulates the men into befriending him and taking vengeance on the three women. So the story goes. Prévan knows that being cheated on publicly is very likely to make the cheatee want payback. This little story whets the Marquise's appetite for revenge of her own.