- There are a lot of system of forming antonyms in English here you will get some nice and easy way.
Un
Able = Unable, Kind = Unkind,
Common = Uncommon, Conscious = Unconscious.
Non
Sense
= Nonsense, Stop = Nonstop, Violence = Nonviolence.
Dis
Agree = Disagree, Honest = Dishonest,
Like = Dislike, Obey = Disobey, Allow = Disallow.
Mal
Practice = Malpractice, Nutrition =
Malnutrition.
Mis
Fortune = Misfortune, Use = Misuse,
Understand = Misunderstand, Conduct
= Misconduct.
Anti
Climax = Anticlimax, Social = Antisocial,
Septic = Antiseptic.
De
Merit
= Demerit, Control = Decontrol, Entrain = Detrain.
Il
Legal = Illegal, Literate = Illiterate,
Logical = Illogical, Legible = Illegible.
Im
Balance = Imbalance, Possible = Impossible,
Personal = Impersonal, Partial = Impartial.
In
Ability
= Inability, Active = Inactive, Valid = Invalid, Accurate = Inaccurate.
Ir
Regular = Irregular, Responsible = Irresponsible,
Rational = Irrational.
Full> Less
Careful = Careless, Hopeful = Hopeless, Faithful = Faithless, Useful = Useless