Jane Austen's novels are fairly fluffy, light reads, and naturally they do not have "villains" as The Lord of the Rings has villains. Most of them do, however, have antagonists - because stories rarely work without them. Having read all of her novels, including her incredibly absurd and highly amusing "Minor Works," I found the differences in her antagonists quite interesting to note; all are smooth-talkers, but their actions and level of villainy differ from one novel to another quite refreshingly.
Pride & Prejudice: Pride and Prejudice boasts Jane Austen's most famous villain in Mr. George Wickham, the unscrupulous officer who charms everyone with his looks and winning ways. He is slippery and conniving - the sort of man most people think of when they think of Austen's antagonists. This is often the first of Austen's novels that people read, so it sets the precedent that if a man seems too good to be true, he will turn out to be the villain.
Sense & Sensibility: Sense and Sensibility (written before Pride and Prejudice) has a similar "antagonist" to Austen's more popular novel. Mr. Willoughby, the charming "suitor" of flighty, romantic Marianne Dashwood, is the quintessential knight in shining armor and fills the role of the tall, dark, and handsome hero that Wickham does in Pride and Prejudice. But though he does resemble Mr. Wickham (Austen seems to have had something against W's), he also has some unique facets. He is a much more tragic sort of character, first of all, and is meant to evoke as much pity as he does anger in the reader - though I confess, I didn't feel particularly sorry for him in the end. Secondly, the story is from Elinor Dashwood's perspective, and since she is less blinded by Willoughby's charms than the rest of her family, he comes across in a different manner than the all-deceiving Wickham.
Emma: This cheery novel does not have a Wickham-like villain, and, indeed, really does not have an antagonist at all, unless it be Emma herself and her matchmaking. It does, however, have the interesting figure Frank Churchill, who especially interested and annoyed me with his selfish, unpredictable ways. I did not know the storyline when first I watched the 1995, Kate Beckinsale production (I read the book after having watched the movie), and so I couldn't be sure how Frank would turn out by the end of it. I found him one of the more interesting Austen antagonists because of that, and also because, selfish though his deception was, he had an understandable reason for his actions that made it almost possible to forgive him.
Persuasion: Persuasion, even more so than Emma, lacked a real villain. In my opinion, the worst antagonist was also the hero - Captain Wentworth, with his offended pride and way of nursing his wrongs. However, that all worked out all right in the end and Wentworth seems to be popular among Janites, so I will say no more.
Northanger Abbey: This novel, different from all of Austen's other works in many regards, shares a feature with Mansfield Park in having two antagonists, brother and sister John and Isabelle Thorpe. John, a friend of the heroine's brother, is anything but the smooth weasel that George Wickham is; he is rough and unlikeable, suited to deceive heroine Catherine Morland, in view of her rather silly, uncritical nature. He is an irritating character, and the fact that he has a chance of winning Catherine's affection makes him more so.
Isabelle, on the other hand, is more subtle and sweet, and thus more poisonous in her influence on Catherine. She is also rather a crude, unladylike character, though, just as her brother is no gentleman. Despite how different they are from the villains of Austen's other works, they are still a thoroughly unlikeable a pair.
Mansfield Park: I left Mansfield Park for last, it having perhaps the most unique style of all of Austen's works, for all its being disliked by many fans of the other novels. It has the brother-sister pair of antagonists that posthumously-published Northanger Abbey does, but Henry and Mary Crawford are far more insidious than the Thorpes. Henry is gentlemanly, though he seems to be more of the Frank Churchill type than the dashing Wickham or Willoughby, and while heroine Fanny Price remains in the dark as to his nature, the reader is aware almost from his entrance into the story that he is unscrupulous. When bent on winning Fanny, Henry's pleasant nature is all the more nerve-wracking for the reader because of Fanny's usual submissiveness and how oblivious the man is whom she truly loves, Edmund Bertram.
But in reading Jane Austen's novels, I thought her best antagonist was Mary Crawford. Mary is everything that Fanny Price is not - charming, vivacious, witty, and also devious, selfish, and unkind - and that mix of charms and vices is one of the best things to have in any villain. She is intriguing in her vivacity, but also hateful in her cruelty; amusing in her wit, but worrisome in her scheming. I have heard others say that they actually liked her better than Fanny, but I found the makeup of her character only served to make her a more stunning antagonist and set her apart from the ranks of Austen's other "villains."