most frightening

alarming appalling atrocious awesome awful chilling daunting dire direful dismaying disquieting dread dreadful fearful fearsome formidable ghastly grabber grim grisly gruesome hair-raising hairy harrowing hideous horrendous horrible horrid horrifying inconceivable intimidating lurid macabre menacing morbid ominous petrifying portentous repellent spooky terrible terrifying traumatic unnerving unspeakable

calming comforting pleasing

daunting disheartening

formidable rebarbative redoubtable

comforting