The antonyms for the word "well-preserved" include terms like deteriorated, decaying, rotting, deteriorating, putrefying, spoiling, decomposing, desiccated, mummified, and withered. These words are used to describe objects, structures, and even people that are in poor condition and show signs of deterioration over time. For example, a decaying building may have chipped paint, crumbling bricks, and broken windows, while a mummified body is dried out and shows signs of decay. These antonyms indicate a lack of care or attention to preservation and often suggest neglect or abandonment. In contrast, well-preserved objects or structures retain their original quality and appearance due to careful maintenance and conservation efforts.