The antonyms, or opposite words for "un-skillfulness" are proficiency, expertise, mastery, skill, and competence. These words describe a person who has the ability to perform a task with a high level of skill, knowledge, and experience. A proficient or skilled person is someone who excels in their field or profession and is known for their expertise. Mastery refers to a level of skill and knowledge that indicates a person has reached the highest level of proficiency in their chosen field or profession. Competence is the ability to perform a task successfully and efficiently, while showing a deep understanding of the skills involved. These antonyms for "un-skillfulness" describe a person who is highly skilled, knowledgeable, and competent in their field or profession.