Antonym of “assuage” is:

The word assuage means to make an unpleasant feeling less intense, to soothe, or to relieve. It implies a reduction in severity or discomfort. Therefore, its antonym must be a word that signifies an increase in intensity or severity. Intensify (A) is the correct antonym because it means to make something stronger, more extreme, or more powerful, directly opposing the act of lessening or relieving. Options B, C, and D are incorrect as they are either synonyms or closely related concepts to 'assuage.' Calm (B) and soothe (D) are direct synonyms, both meaning to make someone or something feel less agitated or distressed. Lessen (C) is also a synonym, meaning to reduce in extent or degree. These choices all describe actions that decrease or alleviate, rather than increase, making 'intensify' the only accurate opposite.