The phrase "most corroded" refers to something that has undergone significant rusting or decay, indicating a state of disrepair. The antonyms for this phrase would be "pristine," "unspoiled," and "immaculate." These words suggest a state of perfection or a condition that is free from damage or decay. Other antonyms could include "polished," "gleaming," "shiny," "lustrous," or "mirror-like," implying a high degree of reflectivity or smoothness. These antonyms provide a stark contrast to the phrase "most corroded" and suggest qualities of cleanliness, brightness, and newness, making them useful to use in a variety of contexts.