The antonyms for the word "more undecayed" are numerous and varied, including "decaying," "rotten," "putrefied," "spoiled," "corroded," "broken down," "disintegrated," "deteriorated," "decomposed," "gone bad," "crumbling," "moldering," "degrading," and "rusty." These words all evoke a sense of decay, decline, or decomposition, and stand in sharp contrast to the idea of something being "more undecayed." Whether referring to physical objects, organic matter, or abstract concepts, these antonyms convey a sense of decline, loss, or decay that can be unsettling or even repugnant to many people.