The antonyms for the word "well-tuned" could be numerous, as it is a word that represents excellence, accuracy, and mastery. Words that can be used as antonyms of "well-tuned" could depend on the context in which it is being used. In terms of music or instruments, the antonyms could be "out-of-tune," "off-key," or "discordant." In terms of cars or machines, the antonyms could be "malfunctioning," "out of alignment," or "unstable." In general, the antonyms could be "uncoordinated," "unmanaged," or "uncontrolled." Therefore, the antonyms for "well-tuned" would represent a lack of precision, organization, or effectiveness.