Protagonists and Antagonists

• Protagonist drives plot forward
• Antagonist tries to stop him

Without a protagonist, the story would be weak and boring as there wouldn't be someone who makes the storyline and drives it. The antagonist is needed to stop the protagonist from reaching their goals.
The antagonist does not necessarily have to be a good guy. It can be either and in some cases both the antagonist and protagonist might be bad or they might both be good. The antagonist just must be able to put obstacles in the way of the protagonist. The antagonist is that who has the most to lose if the goal is achieved.