The word "in-proficient" literally means "not proficient" or "incompetent". Therefore, the antonyms (opposites) for the word "in-proficient" must be words that describe someone as skilled, capable, or proficient. These antonyms include terms such as "competent," "adept," "proficient," "skilled," "expert," "masterly," "capable," and "qualified." These terms describe individuals who possess the necessary skills, knowledge, and experience to excel in their respective fields or undertakings. Individuals who are in-proficient may lack the skills, knowledge, or experience needed to excel in a particular area, and therefore, they would benefit greatly from developing their skills and knowledge.