Antonyms for the phrase "ripening into" could vary depending on the context in which it is used. However, some possible antonyms could include "stunting," "hindering," "delaying," "preventing," or "arresting." These antonyms indicate a lack of progress, growth, or development, in contrast to the natural process of ripening. They could be used to describe a situation where something is not growing or maturing as expected, or to suggest that an obstacle or setback is preventing progress. In contrast, "ripening into" implies a positive process of growth and development, where something is moving towards its full potential.