Use of prefixes like de, dis, in, un, mal can create antonyms as elucidated below for some words starting with alphabet ‘a’. It is worth noting how antonym is not just opposite or negative or absence or removal but more of a negation. Further any particular prefix can denote negations of different kind. The prefix ‘de’ in the case of 'deactivate' and 'detach' is one such instance. Another instance is of prefix ‘in’ in the case of 'inability' and 'inaudible'.
In the following examples of exceptions we will examine how prefixes do not always create antonyms:
Disable and Enable are antonyms but none of them are antonyms of ‘Able’.
Prefix ‘dis’ in ‘Disability’ doesn’t mean that it is antonym of ‘Ability’. Antonym of ‘Ability’ is ‘Inability’. ‘Disability’ means a handicap or a physical or mental condition that limits a person's movements, senses, or activities.
Similarly ‘affect’ and ‘disaffect’ are not antonyms.
Disaffect means
1) to arouse hostility or indifference in where there had formerly been love, affection, or friendliness
2) to alienate the affection, sympathy, support of
3) make discontented or disloyal
China’s policy of aggression and unethical standards has disaffected almost all the countries.
Youth are becoming increasingly disaffected due to culture of violence, apathy and deceit.
Prospect of winning is bleak unless the party takes steps to attract disaffected voters affected by economy.
There is a growing disaffection with the ruling party due to fuel hike, potholed roads, skyrocketing prices of food and vegetables.
Agonistic and Antagonistic are more like synonyms than antonyms.
Agonistic: relates to fight or aggression which is threatening or harmful
Agonistic behaviour is exhibited by territorial species for defending resources from neighbourhood intruders.
Sibling jealousy often leads to agonistic behaviour
Antagonistic: actively showing strong opposition or dislike
Ethnic groups in the city antagonistic to each other over centuries invariably get into a clash during festival processions.
He is extremely antagonistic to all critics and sometimes gets revengeful.
Appoint and Disappoint are another examples which are not antonyms.
‘Disabuse’ is no way related to ‘Abuse’
‘Disabuse’ means: to cause someone no longer to harbour a wrong idea; to free someone from misconception, deception, falsehood, or erroneous belief
After listening to the entire episode she was disabused of her opinion about him whom she used to regard as a gentleman.
A stage comes in everyone’s life when one gets disabused of the fantasy of Santa Clause and with that experience, also loses the innocence of childhood.