The antonyms for the word "most shook-up" could be composed, calm, collected, serene, tranquil, unperturbed, unshaken, unwavering, composed, and peaceful. These words are used to describe a person who is not affected by any external stimuli and is calm and relaxed. In contrast to being "most shook-up," these words indicate a state of inner peace and calmness that is not easily shaken or disturbed. A composed and serene individual is capable of handling challenging situations with grace and ease, while a person who is "most shook-up" might struggle in such circumstances. Therefore, it is essential to strive towards being composed and unruffled, rather than being "most shook-up.