If I have a non-person object or idea that I consider to be my nemesis<sup>1</sup>, how could I refer to the object as a noun but use an embellishing adjective to emphasize that the object is my nemesis?

For instance, "Since the end of World War II, Communism has been the [nemesisical] ideology of the United States."

Some words that come to mind include *adversarial*, *opposing*, *antagonistic*, but these don't have quite the same  meaning.

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<sup>1</sup>This question was prompted by a question on the 'Programmers' Stack: [Do you have a [programming] language that's your nemesis?][1]


  [1]: http://programmers.stackexchange.com/questions/53718/do-you-have-a-language-thats-your-nemesis