— alarm
— alarmed
— alarum
— allurement
— alluring
— appalling
— atrocious
— awful
— baleful
— bloodcurdling
— chilling
— crawly
— creepy
— creepy-crawly
— dire
— direful
— dismaying
— doubtable
— dread
— dreaded
— dreadful
— fearful
— fearsome
— forbidding
— formidable
— frightening
— frightful
— ghastly
— grim
— grisly
— gruesome
— hair-raising
— hairy
— horrendous
— horrible
— horrific
— horrifying
— macabre
— menacing
— minacious
— minatory
— nightmarish
— ominous
— petrifying
— redoubtable
— scarey
— scary
— shivery
— shuddery
— sick
— sinister
— spine-chilling
— stupefying
— terrible
— terrific
— terrifying
— threatening
— ugly
— unnerving