The term "most unexperienced" suggests a lack of familiarity or knowledge in a particular area. Its antonyms are words that imply expertise or mastery in that field. Such antonyms include "most experienced," "well-versed," "knowledgeable," "proficient," "seasoned," and "expert." These words connote a deep understanding and extensive experience in a specific domain. Alternatively, you can also use antonyms such as "skilled," "trained," "practiced," "familiar," "adept," "experienced," and "competent" to describe someone who is capable, accomplished, and proficient in an area of interest. The choice of antonyms depends on the context and the intended meaning of the sentence.