The antagonist in the film Lagaan is Captain Russell, the British officer who imposes the "lagaan" tax on the villagers of Champaner.
Captain Russell is portrayed as a stern and demanding officer who believes in the superiority of the British Empire. He is initially dismissive of the villagers' plight and their attempts to resist the tax. He is also shown to be a skilled and cunning opponent, using his knowledge of the law and his military resources to his advantage.
However, Captain Russell is not entirely a villain. He is also shown to be a man of honor and integrity, respecting the rules of the game he has set up. He is ultimately defeated not by force but by the villagers' ingenuity and their unwavering belief in their cause.
While Captain Russell is the main antagonist, the film also explores other themes of conflict, such as the struggle between tradition and modernity and the clash of cultures. These themes are often embodied in the various characters who interact with the villagers, including the British officers, the local landowners, and the villagers themselves.