detestably

/dɪˈtɛstəbli/
adverb
  1. In a way that deserves or causes strong hatred or disgust; extremely unpleasantly or badly.
    • The villain in the movie behaved detestably, betraying everyone who trusted him.
    • The food was detestably bland, as if it had no seasoning at all.
    • She treated her coworkers detestably, always taking credit for their work.