The antonyms for the term "become able" vary depending on the context in which it is used. Some antonyms may include "incompetent," "unable," "incapable," or "unqualified." These antonyms suggest a lack of skills, knowledge or experience that is required to perform a task, function or job effectively. Other antonyms may include "resign," "quit," or "abdicate." These words denote a sense of giving up, leaving or relinquishing responsibility for something. Ultimately, the antonyms for "become able" are words that describe a lack of ability or readiness to do something effectively or efficiently.