The phrase "being in cahoots with" implies a partnership or collaboration, often with negative connotations. Antonyms for this phrase could include "working against," "competing with," or "opposing." These words suggest a relationship of opposition or conflict, rather than collaboration. Other antonyms could include "acting independently," "diverging from," or "separating from." These words suggest a lack of cooperation or a distancing from others, rather than an active partnership or collaboration. Depending on the context, there may be a range of antonyms that could be used to describe the opposite of being in cahoots with someone.