The phrase "cracking off" can mean various things depending on the context, such as breaking apart or leaving suddenly. To find the antonyms, we need to understand the opposite meaning of each sense. For instance, some antonyms for "cracking" as breaking apart could be joining, fixing, or mending. Meanwhile, the opposite idea of leaving suddenly could be staying, remaining, or settling. So, when used in a different way, "cracking off" can have many different antonyms depending on its meaning within the context. It's important to consider the context to determine which antonyms might be the most accurate to use.