Antagonist

++ Definition:

A character who opposes against the protagonist.

Examples:

1) Joker is a long time villain of batman, he always disagrees or causes havoc which Batman who is the protagonist tries to prevent. Joker is the antagonist because he fights the protagonist.
2) Plankton is a long time villain in the Sponge Bob universe, plankton always tries to steal from our protagonists. He is the antagonist because he goes against the protagonists.

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