Synonyms for Fatal:

adj.

all (adjective)
fateful.
critical, very important (adjective)
decisive.
dangerous (adjective)
risky.
dead (adjective)
departed, Perished, expired, fallen, extinct, Passed, dead, parted, annihilated, deceased.
deadly, lethal (adjective)
deathly, inevitable, destructive, ruinous, terminal, disastrous, cataclysmic, catastrophic, fateful, calamitous, mortal.
destructive (adjective)
cataclysmal, catastrophic, cataclysmic.
ruinous (adjective)
ruinous.

n.

compatible, case-sensitive, clickable, backward-compatible, Antivirus, bursty, asynchronous, best-of-breed, active, compatibility. dire, profound, extreme, momentous, grave, serious, acute, awful, rigorous, desperate, severe, decide. destructive, cataclysmal, help, catastrophic, cataclysmic, ruinous. deadly (noun)
study at deadly.
fatal (noun)
decisive, lethal, disastrous, inevitable, fateful, terminal, black, calamitous, mortal, deathly, unfortunate, deadly.

v.

destroying (verb)
destructive.

Other synonyms:

cataclysmal, catastrophic, cataclysmic. dangerous. momentous, ruinous. injurious
harmful.
Other relevant words:
decisive, harmful, calamitous, dangerous, unsafe, Antivirus, compatible, disastrous, catastrophic, cataclysmic, best-of-breed, dire, inevitable, help, fateful, injurious, acute, mortal, perilous, active, clickable, extreme, serious, grave, lethal, destructive, terminal, severe, deadly, momentous, risky, asynchronous, desperate, cataclysmal, deathly, awful, unfortunate, decide, bursty, ruinous, profound, damaging, live, backward-compatible, hazardous, rigorous, black, case-sensitive, compatibility.

Usage examples for fatal

  1. Yes, there was the fatal spot! – Melomaniacs by James Huneker
  2. That fatal picture had passed through my hands before you saw it. – Fickle Fortune by Elisabeth Burstenbinder (AKA E. Werner)
  3. The consequence of this was fatal to Eliphalet Fox- fatal at least to his prosperity in Gabwrangle. – Quodlibet by John P. Kennedy