The antonyms for "becoming real" include unreal, imaginary, artificial, fake, and illusory. Unreal refers to something that does not exist or lack authenticity. Imaginary involves something that exists only in one's imagination or fantasy. Artificial implies something that is not natural, made by human beings, and often inferior in quality. Fake refers to something that is fraudulent, counterfeit or inauthentic. Illusory involves something that appears to be real but is not.
Overall, the antonyms for becoming real show the absence of authenticity, genuineness, or reality. These words oppose the idea of "becoming real" and imply a lack of truth or authenticity in the object or subject in question.