Thesaurus

abusive, aching, achy, admonishing, admonitory, adverse, agonised, agonising, agonized, agonizing, annihilating, annihilative, bad, baneful, biting, bitter, blasting, breakneck, bruising, burning, calumniatory, calumnious, cancerous, cataclysmal, cataclysmic, catastrophic, caustic, chafed, chanceful, chancy, corrosive, corrupting, counterproductive, critical, crushing, cyanogenetic, cyanogenic, damaging, dangerous, deadly, defamatory, degrading, deleterious, denigrating, denigrative, denigratory, desperate, destructive, detrimental, devastating, dicey, disadvantageous, disapproving, discriminatory, disrespectful, dodgy, erosive, evil, excruciating, galled, harmful, harrowing, hazardous, hepatotoxic, hostile, hurtful, iconoclastic, ill, ill-timed, impolitic, inadvisable, inauspicious, inconvenient, inexpedient, inhumane, injurious, inopportune, insalubrious, insecure, insidious, insubstantial, insulting, invidious, itchy, jejune, libellous, libelous, loathsome, maleficent, malign, minus, mischievous, morbid, mordacious, mordant, nauseating, nauseous, negative, nephrotoxic, nocent, noisome, noxious, offensive, on the hook, opprobrious, ototoxic, painful, parlous, perilous, pernicious, pestilent, poignant, poisonous, precarious, prejudicial, prejudicious, prickling, queasy, racking, ravaging, raw, reproachful, reproving, rich, risky, ruinous, saddle-sore, scurrilous, self-destructive, sensitive, sickening, slanderous, sore, soul-destroying, stabbing, stinging, subtle, suicidal, tender, tingling, torturesome, torturing, torturous, touch-and-go, toxic, toxicant, traumatic, treacherous, uncomplimentary, unfavorable, unfavourable, unhealthful, unhealthy, unkind, unreliable, unsafe, unseasonable, unsound, untimely, untoward, unwholesome, venomous, vesicant, vesicatory, vile, virulent, vitriolic, vulnerable, wasteful, wild, withering, wounding, wrenching, wrong

harmful is a ADJ.