While the Mario series boasts a diverse cast of antagonists, the most prominent and recurring one is Bowser.
He is often depicted as the king of the Koopa race, a group of turtle-like creatures. His primary motives typically involve taking over the Mushroom Kingdom and kidnapping Princess Peach.
Throughout the different games, Bowser has challenged Mario in various ways, using different tactics and schemes to achieve his goals. Despite his persistent attempts, Mario always manages to thwart him and save the day.