baleful

black, bleak, cheerless, chill, cold, comfortless, dark, darkening, depressing, depressive, desolate, dim, disconsolate, dismal, drear, dreary, forlorn, funereal, gloomy, glum, godforsaken, gray (also grey), lonely, lonesome, lugubrious, miserable, morbid, morose, murky, saturnine, sepulchral, somber (or sombre), sullen, wretched

discouraging, disheartening, hopeless, unfavorable, unpromising, unpropitious

ill-fated, ill-starred, star-crossed, troubled, unfortunate, unlucky

evil, malign, malignant

hostile, inimical, unfriendly

contagious, deadly, infectious, infective, pestiferous, pestilent, pestilential, poisonous, venomous

insidious, menacing, ominous, sinister, threatening

hazardous, imperiling (or imperilling), jeopardizing, perilous, risky, unsafe, unsound

nasty, noisome, unhealthful, unhealthy, unwholesome

destructive, fatal, killer, lethal, malignant, ruinous

baneful, deleterious, destructive, harmful, injurious, noxious, pernicious, truculent

infectious, infective, pestilential, poisonous, sublethal, toxic, virulent

dangerous, grave, grievous, hazardous, jeopardizing, menacing, parlous, perilous, risky, serious, threatening, ugly, unhealthy, unsound

bloody, internecine, sanguinary, sanguine