There are many instances scorn and malice between characters, but I will focus on three that jump out at me:
Elizabeth/Darcy: When Darcy is first introduced in chapter three, Elizabeth withheld all negative judgment towards him, observing only that he was of "fine, tall person, handsome features, noble mein, and the report, which was in general circulation within five minutes after his entrance, of his having ten thousand a year." In short, he is an extremely handsome, extremely rich, and very single man, and there was- at first- nothing to dislike. However, Darcywas used to travelling in circles of much higher wealth and breeding, and so disliked the company that he was in that he insulted Elizabeth before he even knew her, saying "She is tolerable, but not handsome enough to tempt me; and I am in no humor at present to give consequence to young ladies who are slighted by other men. You had better return to your partner and enjoy her smiles, for you are wasting your time with me." From this point, Elizabeth was determined to dislike Darcy, and Darcy- though he quickly realized that Elizabeth was far more beautiful, brilliant and sophisticated than he had granted her credit- continued to believe that he would be demeaning himself to stoop so low as tohimself to marry her, and even his first proposal to her came with great reluctance. Elizabeth's own scorn towards Mr. Darcy pushed her to immediately believe the malicious lies that Mr. Wickham told her about Darcy's "wickedness", though she hardly knew anything at all about Darcy and refused to seek his side of the story. In fact, none of this is resolved until Darcy saves Elizabeth's sister, Lydia, from the danger of an irrevocably damaged reputation due to her indescretion with Mr. Wickham, and Elizabeth and Darcy realize that their prejudices against one another were totally unjust and they allow themselves to fall deeply in love and eventually marry.
Miss Bingly/Elizabeth: Though not nearly as dramatic or undeserving as the contemptuousness between Elizabeth and her future husband, the hatred between Miss Bingley and Elizabeth Bennet tells the age-old tale of female jealousy. Caroline Bingley, a wealthy woman who grew up in the rich society of London and her heart set on Fitzwilliam Darcy, hates two things: country people with common ancestry, and rivals for Mr. Darcy's affections. Unfortunately, Elizabeth Bennet happens to be both. Miss Bingley despises Elizabeth, and expends much of her time and energy trying to incite Darcy to feel the same. Each time that Darcy extends a compliment towards Elizabeth,Miss Bingley becomes more enraged and jealous. Elizabeth, too, feels scorn towards Caroline, but this is simply for Miss Bingley's mean and catty behavior.
Darcy/Wickham: Mr. Darcy hates Mr. Wickham because Mr. Wickham is a self-serving, dishonest person. The two men were raised together,and lived like brothers for much of their young life. Upon the death of Mr. Darcy's father, Wickham ran himself into debt, squandered his inheritance, threw away two career opportunities,and attempted to marry the young and impressionable sister of Mr. Darcy simply so that he could control her money. After Darcy had squashed his plans, Wickham took to spreading terrible lies about Darcy and how he had supposedly left him bereft and ruined his life simply for spite. Indeed, many people believed him, and Wickham's true nature was not revealed until the business with Lydia Bennet.