nemesis

noun6

1. •
   An enemy, especially an archenemy.

   • Batman is in constant conflict with his nemesis, The Joker.
2. •
   The principle of retributive justice.
3. •
   (formal) A punishment or defeat that is deserved and cannot be avoided; (an instance of) retribution.
4. •
   A person or character who specifically brings about the downfall of another person or character, as an agent of that character's fate or destiny, especially within a narrative.
5. •
   Polar opposite, especially of a literary character.
6. •
   The personification of the "fatal flaw" of a dramatic hero in the style of Greek tragedy.