The words that could be considered opposite or antonyms of "take turn for better" are phrases that describe an overall decline or worsening situation. Words like deteriorate, decline, worsen, regress, backslide, falter, slump, or degenerate all suggest that things are getting worse, rather than improving. These terms can be applied to many different scenarios, from personal health to political situations, economic progress or environmental sustainability. While taking a turn for the better is always preferable, it's important to be aware of the potential for things to take a negative turn as well, so that we can be prepared to take action and mitigate any negative effects.