Mismanager is a term used to describe a person who is incapable of managing or handling things properly. The antonym of this word can have several different interpretations, depending on the context in which it is used. In general terms, antonyms for mismanager might include words like "competent," "efficient" or "successful." These are all terms that describe someone who is skilled at managing tasks, resources or personnel, and who is able to achieve positive outcomes through their efforts. Other antonyms for mismanager might be more specific, such as "leader," "organizer," "planner" or "director." These are all roles or titles that suggest a person who is capable of assuming responsibility for a group or project and guiding it towards success.