The phrase "most rosy-cheeked" implies someone with a healthy complexion and a bright, cheerful demeanor. However, there are many antonyms to describe the opposite of this phrase. Some of these antonyms might be pale, sallow, wan, unhealthily thin, or depressed.
A person who is pale or sallow might be suffering from an illness or a lack of exposure to sunlight, while someone who is unhealthily thin may look tired and gaunt. Meanwhile, a person who is depressed may appear sad or disinterested in their surroundings, and their cheeks might even appear sunken.
In contrast to a "rosy-cheeked" individual, someone who is described with one of these antonyms might not exude confidence or happiness.