embitterest

Verb

embitter (third-person singular simple present embitters, present participle embittering, simple past and past participle embittered)

1. (archaic, transitive) To cause (something) to be or taste bitter; to bitter.

   Synonyms:

   acerbate

2. (figuratively, transitive) To cause (a positive quality such as happiness, or a thing such as an activity or one's life) to become less good or pleasurable; also, to make (a negative quality, or thing such as a disagreement) worse or more unpleasant.
   • He imbitters not a diſtaſtfull meſſage to a forrein Prince by his indiſcretion in delivering it.1642, Thomas Fuller, “The Good Herald”, in The Holy State, Cambridge, Cambridgeshire: […] Roger Daniel for John Williams, […], →OCLC, book II, paragraph 2, page 142
3. (figuratively, transitive) To cause (someone or their feelings) to become more angry, resentful, or unfriendly; to envenom.
   • Sometimes it [pride] ſtirreth vp men, and imboldeneth them to offer vvrongs: ſometimes imbittereth men; and maketh them vvayvvard againſt the right: […]1608, John Dod, Robert Cleaver, “Chapter XIII. [Vers[e] 10. Through mere pride doth man make contentions; but with the well aduised is wisedome.]”, in A Plaine and Familiar Exposition of the...