The antonyms of "un-developed" are "developed" and "progressive." Developed refers to something that is well-constructed or advanced, while progressive is associated with growth and change. Both terms are often used to describe a country, economy, or individual who has achieved significant progress and advancement in their respective fields. Developed nations are categorized by their high standards of living, advanced infrastructure, and high levels of innovation, while progressive individuals display a forward-thinking mentality and a willingness to adapt to different situations. In contrast, the opposite of un-developed lacks progress or advancement and can be a term used to describe outdated, primitive, or archaic structures or ideas.