What is the opposite of promoting someone's reputation?

The opposite of promoting someone's reputation is denigrating. When you promote someone's reputation, you are enhancing or improving how others perceive them, often by highlighting their positive qualities, achievements, or character. Denigrating, on the other hand, involves speaking critically or disparagingly about someone, which undermines their reputation and can lead to a tarnished perception in the eyes of others. This choice clearly captures the idea of acting against someone's reputation as opposed to enhancing, praising, or protecting it, which are all ways of positively reinforcing one's standing.