Malign seems great, but it carries connotations of deliberate evil (like "malevolent").

Fatal or terminal might work, but aren't specific enough.

  • 2
    Why one word? Please supply sentence with blank,
    – Xanne
    Aug 22, 2019 at 6:33
  • 1
    What do you mean by ‘universally’ fatal? Do you mean that it will always cause death (e.g., lack of oxygen), or that it will cause death on a universal scale (e.g., giant meteor hitting the earth, wiping out life as we know it)? Aug 22, 2019 at 7:25
  • Context would also indicate whether a word referencing a specific kind of death would fit, such as "toxic" (which refers to poisoning), or "terminal" (which refers to illness).
    – Stuart F
    Aug 22, 2019 at 16:27

2 Answers 2


In my experience the word Lethal may be a good choice here.


Three words starting with C in a roughly ascending order of magnitude.

calamitous - a serious accident or bad event causing damage or suffering

catastrophic - a sudden event that causes very great trouble or destruction

cataclysmic - an event that causes a lot of destruction, or a sudden, violent change

Definitions courtesy of Cambridge Dictionary

Not the answer you're looking for? Browse other questions tagged or ask your own question.