Antonyms for the phrase "treat badly" could include "kindly," "respectfully," "fairly," "nicely," "generously," and "compassionately." When someone is treated badly, they are often subjected to negative behavior, such as rudeness, neglect, or abuse. The opposite of such behavior would be to treat someone with warmth, consideration, and empathy. For instance, instead of treating someone badly because they made a mistake, you could offer encouragement and support, showing them kindness and understanding. By treating others kindly and respectfully, we can foster positive relationships and create a better world.