Synonyms for Deadly:

adj.

all (adjective)
deathly, mortal.
causing end of life (adjective)
fatal, baneful, deathly, mortal, toxic, malignant, injurious, violent, homicidal, venomous, deleterious, destructive, lethal, pernicious, murderous, dangerous, noxious, cannibalistic, virulent, harmful, bloody, pestilent, bloodthirsty, poisonous, suicidal.
communicable (adjective)
contagious.
dangerous (adjective)
risky, pestilent.
destructive (adjective)
deleterious, devastating, damaging, destructive, calamitous, injurious, disastrous, harmful, detrimental, catastrophic.
diseased (adjective)
malignant.
ghostly (adjective)
ghastly.
harmful (adjective)
poisonous.
murderous (adjective)
murderous, homicidal.
unhealthy (adjective)
contagious, poisonous, toxic, gangrenous, contaminated, unhealthy, pestilent, unwholesome, unhygienic, infected, diseased, insalubrious, pathological, unsanitary, malignant, septic, noxious.

adv

extremely (adverb)
extraordinarily, outstandingly, exceedingly, extremely, distinctly, unusually, overwhelmingly, supremely, incredibly, enormously.

adv.

all (adverb)
lifelessly.

n.

hazardous, unsafe, boring, tedious, tiresome, dull, perilous, risky. help. deadly (noun)
harmful, lifelessly, fatal, baneful, madly, deucedly, lethal, pernicious, toxic, unpardonable, virulent, mortal, pestilent, deathly, venomous, insanely, devilishly, noxious.

v.

destroying (verb)
murderous.

Other synonyms:

ghostlike. dangerous, cadaverous, spectral. ghostly. dull, ghastly. fatal
fatal.
lethal
lethal.
self-destructive
suicidal.

Usage examples for deadly

  1. Constance turned deadly pale: her frame trembled; but she did not answer immediately. – Godolphin, Volume 2. by Edward Bulwer-Lytton
  2. Those deadly termites were on the move! – Spawn of the Comet by Harold Thompson Rich
  3. But you often tell us to be serious, to be deadly earnest, about our work? – Father Payne by Arthur Christopher Benson