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Oh, Chillingworth. Of course you would choose such a frosty pseudonym when you're getting ready to track down your wife's lover and persecute him in secret for seven years. That's just the kind of guy you are.
You have to give him credit for perseverance, at least. He did love Hester at one point, so much that he managed to convince her to marry him, even though he was (1) old, and (2) a scholar and intellectual. Later he regrets this, calling it a "folly" to want to marry a beautiful young woman, but too bad, so sad: he doesn't regret it in time to stop three lives from being ruined. (Also, dude: if you've just married a young pretty wife, what are you doing sending her across the ocean by herself and then not showing up for two years?)
And now, Shmoopers, brace yourselves for Roger Chillingworth in action:
Yea, woman, thou sayest truly!" cried old Roger Chillingworth, letting the lurid fire of his heart blaze out before her eyes. "Better had he died at once! Never did mortal suffer what this man has suffered. And all, all, in the sight of his worst enemy! He has been conscious of me. He has felt an influence dwelling always upon him like a curse. He knew, by some spiritual sense,—for the Creator never made another being so sensitive as this,—he knew that no friendly hand was pulling at his heart-strings, and that an eye was looking curiously into him, which sought only evil, and found it. But he knew not that the eye and hand were mine! With the superstition common to his brotherhood, he fancied himself given over to a fiend, to be tortured with frightful dreams, and desperate thoughts, the sting of remorse, and despair of pardon; as a foretaste of what awaits him beyond the grave. But it was the constant shadow of my presence!—the closest propinquity of the man whom he had most vilely wronged! —and who had grown to exist only by this perpetual poison of the direst revenge! Yea, indeed!—he did not err!—there was a fiend at his elbow! A mortal man, with once a human heart, has become a fiend for his especial torment! (14.18)
Here, Chillingworth is telling Hester exactly how miserable he's making Dimmesdale. (Pretty miserable.) But check out the way he does it—with "lurid fire," lots of "Yea, woman," and nine exclamation marks. This isn't just your ordinary Cheaters moment. This is hellfire-and-damnation, I-will-haunt-you-to-your-grave talk.
To be honest, Chillingworth is a bit of a one-note character: revenge has turned him from a dry, unassuming scholar into a hellish "fiend" whose sole purpose is to psychologically torture Dimmesdale. Once Dimmesdale is dead, he no longer has a reason to live.
But there are two little things about Chillingworth that make us go "huh."
(1) One of the reasons he took so long in showing up to the colony is that he was help captive by American Indians, where he "had gained much knowledge of the properties of native herbs and roots… [which] had quite as large a share of his own confidence as the European Pharmacopoeia" (9.2). Translation? He trusts native medicine, which, for a white guy in the mid-17th century, means that's he's got a surprisingly open mind.
(2) When he dies, he leaves a fortune to Pearl, who becomes the "richest heiress of her day in the New World." Why? What could possibly possess this man to leave his fortune to the daughter of his mortal enemy and the wife who cheated on him? Has he learned some sort of lesson? Is it an apology to Hester? To Dimmesdale?