Grievous

1. adjective

   of great gravity or crucial import; requiring serious thought

   “grave responsibilities”

   Similar: grave, heavy, weighty

2. adjective

   causing fear or anxiety by threatening great harm

   “a dangerous operation”

   Similar: dangerous, grave, serious, severe

3. adjective

   causing or marked by grief or anguish

   “a grievous loss”

   Similar: heartbreaking, heartrending

4. adjective

   shockingly brutal or cruel

   “murder is an atrocious crime”

   Similar: atrocious, flagitious, monstrous