The true opposite of prefix is no prefix.
But, as a prefix means something added at the start of a word. the generally understood opposite is suffix - which is something added to the end of a word.
The prefix un- makes the word "unsuitable."
The opposite is impatient.
The opposite prefix of "incredible" is "cred." The prefix "in-" indicates negation or the opposite, so removing it leaves "credible," which means believable or able to be trusted. Thus, "credible" serves as the antonym of "incredible."
The prefix "dif means the opposite of, or reverse.
The prefix 'dis' means not or the opposite of something.
The opposite prefix of the prefix "meta-" is "pre-".
The opposite prefix for personal is "impersonal."
The opposite of median with a prefix is "nonmedian."
The opposite prefix of "essential" is "non-essential."
The opposite of active using a prefix is "inactive."
The opposite of "thoughtful" with a prefix would be "thoughtless."
The prefix for the opposite of order is "dis-" or "un-".
The opposite of judge using a prefix is misjudge.
The opposite prefix of "distinct" is "in-," making the word "indistinct."
The opposite form of the word "expendable" by adding a prefix is unexpendable.
The opposite prefix to "lawful" is "un-," so the opposite of "lawful" would be "unlawful."
The opposite prefix of "reverent" is "ir-" or "dis-", so the opposite could be "irreverent" or "disrespectful".