The function of the antagonism is to force the hero to overcome limitations. This does not necessarily mean it must be defeated.
In Moneyball (2011), the Red Sox owner forces Beane to make the decision between money / Boston and Oakland / his daughter.
However, commonly, the Capacity to repress / defeat / destroy the antagonism is a measure that limitations have been overcome. If the antagonism is an obstacle to the State of Perfection, then it is defeated.
In Return of the Jedi (1983), the Emperor is defeated.
In The Lord of the Rings: The Return of the King (2003), Sauron is defeated.
In Harry Potter and the Deathly Hallows: Part 2 (2011), Voldermort is defeated.
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