The protagonist in the novel is obviously Huck Finn. He is the narrator of the story and the character who changes the most in the novel. If you need an antagonist, it would be the entire Southern system of slavery and the evils that came with it. Since the novel is told in episodes as Jim and Huck float down the Mississippi River, there are also other antagonists along the way. At first, Pap threatens to kill Huck. Miss Watson is going to sell Jim. Slave hunters want to capture Jim and return him for a reward. The King and the Duke want to con the Wilkes sisters and Huck must take action to save them. In addition, the King sells Jim. Finally, Tom Sawyer becomes a minor antagonist when he arrives at the Phelps plantation because he romantic ideas of how to free Jim put Jim in danger. This is made even more cruel because Tom actually knows Jim is already free and he just wants adventure. Thus Huck must face several antagonists during his journey to freedom.