A character that is always against the interest of the protagonist is

A character that is always against the interest of the protagonist is known as the "villain". The villain is a character in a story who acts as the main source of conflict and obstacle for the protagonist. Their primary purpose is to create tension and challenge the hero, often by causing harm, creating obstacles, or opposing the protagonist's goals. The villain is usually portrayed as malicious, cruel, or immoral, and they are a constant threat to the hero's well-being and success. In many stories, the hero and the villain engage in a battle of wills, where the hero must use their skills, intelligence, and determination to overcome the villain's actions and ultimately achieve a favorable outcome. The villain is an essential element in storytelling, as they provide a contrast to the hero and offer opportunities for growth, redemption, and triumph.