calamitous
1. [ adjective ] (of events) having extremely unfortunate or dire consequences; bringing ruin
Synonyms: disastrous black fateful fatal
Examples:

"the stock market crashed on Black Friday" "a calamitous defeat" "a disastrous end to a disastrous campaign" "this would be absolutely fatal to my theory"

Related terms: unfortunate
Similar spelling:   calamity
  calamity_jane