Adjectives

(a)fatalbringing death
(s)fateful, fatalhaving momentous consequences; of decisive importance“that fateful meeting of the U.N. when … it declared war on North Korea” (Saturday Rev), “the fatal day of the election finally arrived”
(s)black, calamitous, disastrous, fatal, fateful(of events) having extremely unfortunate or dire consequences; bringing ruin“the stock market crashed on Black Friday”, “a calamitous defeat”, “the battle was a disastrous end to a disastrous campaign”, “such doctrines, if true, would be absolutely fatal to my theory” (Charles Darwin), “it is fatal to enter any war without the will to win it” (Douglas MacArthur), “a fateful error”
(s)fatal, fatefulcontrolled or decreed by fate; predetermined“a fatal series of events”