alarming
atrocious
awful
daunting
demoralizing
dire
direful
disconcerting
discouraging
dismaying
disquieting
distressing
disturbing
dread
dreadful
dreadful
fearful
fearsome
forbidding
foreboding
formidable
frightening
frightful
ghastly
grisline
gruesome
hair-raising
hideous
horrendous
horrible
horrid
horrifying
intimidating
monstrosity
perturbing
redoubtable
repulsive
shocking
spine-chilling
startling
terrible
terrifying
threatening
troubling
trying
unnerving