Option 1: Ameliorate -> means to make better or improve; similar to assuage.
Option 2: Conciliate -> means to pacify or reconcile; similar to assuage.
Option 3: Placate -> means to calm or appease; similar to assuage.
Option 4: Exacerbate -> means to make worse or intensify; opposite to assuage.
Hence, Option 4: Exacerbate -> "Assuage" means to ease or lessen something unpleasant (like grief), while "exacerbate" means to make it worse or more severe, making them antonyms -> correct