Preconize means to promote, advertise or praise highly, and some of its antonyms include criticize, condemn, degrade, belittle and disparage. While preconize refers to promoting something or someone highly, criticize, condemn, and degrade imply the opposite, meaning to express negative opinions or disapproval. Belittle and disparage, on the other hand, specifically suggest diminishing or downgrading the value or importance of something or someone. As with many words, the antonyms of preconize may vary depending on the context, but these are some common ones that are often used.