The antonym of "most compressed" is "least compressed". When something is "least compressed", it means that it is not compressed enough or not compressed at all. It could also imply that it has more space or volume, compared to its compressed state. For example, a spring that is least compressed can be stretched, while a compressed spring has less flexibility. Another example would be a document file that is least compressed, which means it has a larger file size and takes up more storage space. In summary, the antonym of "most compressed" describes something that is not squeezed or condensed, either physically or digitally.