The word "re-condition" means to restore to a good or usable condition, but there are several antonyms to this term. One antonym is "deteriorate," which means to decline or become worse in condition. Another antonym is "degrade," which refers to lowering the quality or condition. "Decline" is another antonym that means to lessen or become weaker in condition. "Corrupt" is another antonym that refers to a decline in moral or ethical standards. Finally, "ruin" is an antonym that means to completely destroy or make something unusable. These antonyms highlight the opposite of the action of "re-conditioning", which is to make something better or usable again.