Reprisal (Noun)
Synonym: retaliation, counterattack
Antonym: pardon, remission
Meticulous (adjective)
Synonym: careful, conscientious
Antonym: careless, sloppy, slapdash
Unprecedented (adjective)
Synonym: unequalled, unmatched, unrivalled
Antonym: precedented, familiar, usual
Conducive (adjective)
Synonyms: Good for, Helpful, Instrumental in, calculated to produce, favourable
Antonym: Unfavourable
Fester (Verb)
Synonyms: Suppurate, Rot, Decay, Degrade, Disintegrate
Antonym: Build, Grow, Please, Improve, Flourish