Most copacetic refers to something that is agreeable or satisfactory. Antonyms for this phrase would be words that describe something that is unpleasant or unsatisfactory. Some possible antonyms for most copacetic could be disagreeable, unpleasant, irksome, distasteful, or problematic. These words refer to things that are not easy to endure or have negative qualities that make them unacceptable. For instance, an individual may find their job most copacetic, but the work environment could be characterized as irksome, which is an antonym for copacetic. Likewise, most copacetic can also be the antonym of words like unsatisfactory or inadequate, which describes something as being below expectations.