The antonyms for the phrase "lost luster" are numerous, but the most common ones are "sparkling," "shiny," "glossy," "polished," "gleaming," "radiant," "bright," and "lustrous." These words could be used to describe objects that look glittery or polished. They could also be applied to people or things that are full of energy, enthusiasm, and vitality. The opposite of "lost luster" could also be expressed through words such as "vibrant," "alive," "vivid," "dynamic," and "flourishing." These antonyms are useful for describing situations in which something has been revitalized or restored to its former glory after a period of decline or neglect.