Larxene from Kingdom Hearts is a prime example of this trope, but in a grown-up group setting. She is mean to both ally and enemy alike, and is an absolute sadist. Her sadistic and sarcastic comments as well as actions often harasses her own allies, particularly the resident dork Demyx, whom she also has doing favors for her against his liking. However, her behavior is probably due to her lack of emotions combined with a painful past life from back when she did have them.
Mandy Wiles in Bully. Head cheerleader and self-proclaimed most popular girl in school, who mercilessly torments nerd girl Beatrice and humiliates people for her own amusement. A subversion, though, in that her friends claim that she's actually nice once you get to know her. And then, late in the game, she gets a Pet the Dog moment.
Derby Harrington, leader of the preppies, may also count as a male example. He's rich, entitled, and condescending towards the player even after you defeat him and his clique.
Krista Sparks (aka Dollface) in the 2012 reboot of Twisted Metal is this character all grown up and taken to a psychopathic/Ax-Crazy degree. She feels that she deserves to become a supermodel due to her hard work... her definition of which includes sabotaging her rivals and, at times, outright murdering them.
Yume Miru Kusuri: Kyoka — called "Antoinette" by the main character, after the infamous French queen whose extravagant spending on things such as mansions and the like (although a lot of it was exaggerated by enemies) while people were starving out on the fields was a prime example of the kind of thing that led to the French Revolution — is the antagonist of Aeka's route. Something that's kind of odd to this trope is that she had a crush on the lead from the beginning and tried to get with him several times, though the lead just found her annoying. This doesn't stop her from targeting him along with Aeka once it becomes official that the two are going out, though. It gets pretty brutal. This goes for the backlash, as well, which sees Kouhei and Aeka turn the tables on and nearly kill Kyoka when she decides to have her friends pin down Kouhei so that he can watch Kyoka's boyfriend rape Aeka.