ameliorate

This term is primarily used in formal, academic, or bureaucratic contexts to describe the improvement of a negative state. It carries a clinical or systemic tone, often appearing in discussions regarding social policy, legal reforms, or medical treatments where the goal is to mitigate suffering or rectify a deficiency.

While similar to "improve," it specifically implies that the starting point was poor, unsatisfactory, or oppressive. One does not typically ameliorate a good situation to make it great; rather, one ameliorates a dire situation to make it tolerable or acceptable.