General:
* Provoke
* Irritate
* Exasperate
* Infuriate
* Harass
* Bait
* Goad
* Pester
* Challenge
* Spar
More specific:
* Alienate: To make someone feel isolated or estranged.
* Incite: To encourage or stir up hostile feelings.
* Oppose: To actively resist or disagree with something.
* Counteract: To act against or neutralize something.
* Subvert: To undermine or overthrow something.
* Defy: To refuse to obey or comply with something.
Informal:
* Pick a fight with
* Get on someone's nerves
* Push someone's buttons
* Rub someone the wrong way
The best synonym for "antagonize" depends on the specific context and the intended meaning.