bloodcurdling

alarming, dire, direful, fearful, fearsome, forbidding, formidable, frightening, gut-wrenching, hair-raising, heart-stopping, intimidating, redoubtable, scary, terrifying

appalling, atrocious, awful, dreadful, frightful, ghastly, grisly, gruesome (also grewsome), hideous, horrendous, horrible, horrid, horrific, horrifying, lurid, macabre, monstrous, nightmare, nightmarish, shocking, terrible, terrific

abhorrent, deplorable, disagreeable, disgusting, distasteful, loathsome, nauseating, noisome, obnoxious, obscene, offensive, repugnant, repulsive, revolting, sickening

abominable, evil, foul, heinous, noxious, odious, unspeakable, vile

grotesque, ugly, unsightly