Word Study
harmful
OXFORD DICTIONARY
harmful, adj. causing or likely to cause harm.
Derivative
harmfully adv. harmfulness n.
THESAURUS
harmful
adverse, antagonistic, bad, bad for, baleful, baneful, bitchy, conflicting, contaminated, contrary, corroding, corrosive, corrupting, corruptive, counter, counteractive, counterproductive, cussed, damaging, dangerous, deadly, deleterious, destructive, detrimental, difficult, disadvantageous, disserviceable, distressing, evil, foul, hard, hateful, hazardous, hostile, hurtful, ill, in opposition, inimical, iniquitous, injurious, insalubrious, insanitary, invidious, lethal, malefic, maleficent, malevolent, malicious, malign, malignant, mean, mischievous, miserable, morbific, nasty, noisome, not easy, noxious, ominous, opposed, opposing, opposite, ornery, pathogenic, peccant, pernicious, pestiferous, poisonous, polluted, prejudicial, rigorous, risky, scatheful, septic, sinister, stressful, tainted, toxic, troublesome, troublous, trying, unadvantageous, unfavorable, unhealthful, unhealthy, unhygienic, unprofitable, unrewarding, unsafe, unsanitary, untoward, unwholesome, useless, venenate, veneniferous, venenous, venomous, vicious, virulent, wicked, worthless, wretchedROGET THESAURUS
harmful
Badness
N badness, hurtfulness, virulence, evil doer, bane, plague spot, evil star, ill wind, hoodoo, Jonah, snake in the grass, skeleton in the closet, amari aliquid, thorn in the side, malignity, malevolence, tender mercies, ill-treatment, annoyance, molestation, abuse, oppression, persecution, outrage, misusage, injury, knockout drops, badness, peccancy, abomination, painfulness, pestilence, guilt, depravity, hurtful, harmful, scathful, baneful, baleful, injurious, deleterious, detrimental, noxious, pernicious, mischievous, full of mischief, mischief-making, malefic, malignant, nocuous, noisome, prejudicial, disserviceable, disadvantageous, wide-wasting, unlucky, sinister, obnoxious, untoward, disastrous, oppressive, burdensome, onerous, malign, corrupting &c (corrupt), virulent, venomous, envenomed, corrosive, poisonous, deadly, destructive, inauspicious, bad, ill, arrant, as bad as bad can be, dreadful, horrid, horrible, dire, rank, peccant, foul, fulsome, rotten, rotten at the core, vile, base, villainous, mean, injured, deteriorated, unsatisfactory, exceptionable indifferent, below par, illcontrived, ill-conditioned, wretched, sad, grievous, deplorable, lamentable, pitiful, pitiable, woeful, evil, wrong, depraved, shocking, reprehensible, hateful, hateful as a toad, abominable, detestable, execrable, cursed, accursed, confounded, damned, damnable, infernal, diabolic, unadvisable, unprofitable, incompetent, irremediable, badly, wrong, ill, to one's cost, where the shoe pinches, bad is the best: the worst come to the worst, herba mala presto cresco, wrongs unredressed or insults unavenged.For further exploring for "harmful" in Webster Dictionary Online