Unsocial, asocial, antisocial, nonsocial are comparable in meaning not social and therefore opposed in some way to what is social.
However, they are not ordinarily interchangeable.
Unsocial is applied chiefly to persons or to their temperaments, acts, and motives, and implies a distaste for the society of others or an aversion to companionship or fraternization.
Asocial is also applied to persons, but especially to their behavior, their thoughts, or their acts regarded objectively (as from the psychologist’s point of view); it implies a lack of all the qualities which are suggested by the word social especially as opposed to individual .
What is asocial lacks reference to, or orientation towards or in respect to, or significance for others and is by implication, individualistic, self-centered, egocentric, or egoistic.
Antisocial is applied chiefly to things (as ideas, movements, acts, or writings) which are regarded as harmful to or destructive of society or the social order or institutions (as the state and church).
Nonsocial is applied only to things which cannot be described as social in any sense of the word.