alarming, dire, direful, dread, dreadful, fearful, fearsome, forbidding, formidable, frightening, frightful, ghastly, hair-raising, horrendous, horrible, horrifying, intimidating, redoubtable, scary, shocking, terrible, terrifying

daunting, demoralizing, disconcerting, discouraging, dismaying, disquieting, distressing, disturbing, perturbing, startling, threatening, troubling, trying, unnervingbone-chilling, creepy, eerie(also eery), weirdappalling, atrocious, awful, grisly, gruesome(also grewsome), hideous, horrid, macabre, monstrous, nightmarish

calming, comforting, consoling, inviting, lulling, pacifying, quieting, reassuring, relaxing, soothing, tranquilizing(also tranquillizing)nonintimidating, nonthreatening