The term "more ungrown" implies a lack of maturity or development. Therefore, some antonyms for this phrase could include "fully grown," "mature," "developed," "experienced," "sophisticated," "ripe," or "seasoned." These words convey a sense of completeness, refinement, and accomplishment that is the opposite of immaturity or inexperience. Using these antonyms can help you convey a more positive and nuanced message to your audience, highlighting the qualities that you admire and respect in others or yourself. So, when you want to describe someone who is not "more ungrown," consider using one of these antonyms instead.