Monstrous
Part of speech: adjective
Definition: hideous or frightful enormously large freakish or grotesque of, or relating to a mythical monster
Example sentence: The most shocking fact about war is that its victims and its instruments are individual human beings, and that these individual beings are condemned by the monstrous conventions of politics to murder or be murdered in quarrels not their own.
Grievous
Part of speech: adjective
Definition: Causing grief, pain or sorrowserious, grave, dire or dangerous