The phrase "clean up act" is widely used to describe the action of improving or rectifying one's behavior or situation. However, there are several antonyms for this phrase that depict the opposite circumstances. "Mess up act" might indicate a situation where things are end up in a chaotic state due to careless behavior. "Screw up act" suggests a disastrous action or event that leads to failure or disappointment. "Break down act" implies a situation where something suddenly stops working or fails to operate properly. All these antonyms paint a picture of unruliness, disorder, and failure, in contrast to the positive connotation of "clean up act".