An antagonist is the character in a story who stands in opposition towards the protagonist. As an example, in the Disney movie The Lion King, the main antagonist is Scar.

While the most common practice is for a hero to be the protagonist and the villain to be the antagonist this is not always the case. As an example in the manga/anime series Death Note protagonist Light Yagami was the villain as it was his goal to rid the world of criminals in order to create his own ideal "utopia" and rule it like a god while antagonist L was the hero as it was his goal to end Light's psychotic killing spree. Another example is Sweeney Todd: The Demon Barber of Fleet Street where the titular protagonist and the antagonist Judge Turpin were both villains.