fatal fatal /ˈfeɪtəl/

adjective

1. () Bringing death  ( fatal )
   bringing death
     The fatal accident resulted in multiple casualties.
   The fatal accident resulted in multiple casualties.
   
2. () Having momentous consequences; of decisive importance  ( fateful , fatal )
   having momentous consequences; of decisive importance
    That fateful meeting of the U.N. when...it declared war on North Korea
   that fateful meeting of the U.N. when...it declared war on North Korea
    The fatal day of the election finally arrived
   the fatal day of the election finally arrived
   
3. Controlled or decreed by fate; predetermined  ( fatal , fateful )
   controlled or decreed by fate; predetermined
    A fatal series of events
   a fatal series of events
   
4. (of events) having extremely unfortunate or dire consequences; bringing ruin  ( calamitous , fatal , fateful , black , disastrous )
   (of events) having extremely unfortunate or dire consequences; bringing ruin
    The stock market crashed on Black Friday
   the stock market crashed on Black Friday
    A calamitous defeat
   a calamitous defeat
    The battle was a disastrous end to a disastrous campaign
   the battle was a disastrous end to a disastrous campaign
    Such doctrines, if true, would be absolutely fatal to my theory
   such doctrines, if true, would be absolutely fatal to my theory
    It is fatal to enter any war without the will to win it
   it is fatal to enter any war without the will to win it
    A fateful error
   a fateful error