The antonyms for the phrase "becoming firm" are "weakening," "softening," "yielding," "flexible," and "pliable." These terms indicate a lack of strength, hardness, and resistance. A person who is weak or flexible cannot become firm or strong. Similarly, a material that is yielding or pliable cannot maintain its shape or withstand pressure. In contrast, becoming firm implies progress, determination, and growth. It suggests that a person is evolving towards their goals, improving their skills or talents, or strengthening their character. Therefore, the antonyms for becoming firm are not desirable traits unless they serve a specific purpose or context.