Synonyms of lethal

2 Syllables
deadliest, fatal, deadlier, wreckful, septic, toxic, harmful, noxious, deadly, mortal, deathly, hurtful
3 Syllables
pernicious, sanguineous, slaughterous, death-dealing, terminals, baleful, murderous, viperish, necrotic, toxicant, venomous, poisonous, dangerous, mortuary, pestilent, hellfire, terminal, suicidal, miasmatic, virulent, malignant
4 Syllables
lethiferous, homicidal, insalubrious, pestilential, unnutritious, destructive, mephitical, mortiferous, devastating
5 Syllables
extirpative, unwholesome, fire-and-brimstone
6 Syllables
eradicative