appalling
atrocious
awful
baleful
bloodcurdling
chilling
creepy
creepy-crawly
dire
direful
dismaying
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
stupefying
terrible
terrific
terrifying
threatening
ugly
awing
bad
critical
dangerous
dangersome
daunting
deterrent
deterring
disconcerting
discouraging
disheartening
disquieting
explosive
fear-inspiring
fraught with danger
ghastful
jeopardous
overawing
parlous
periculous
perilous
scaring
serious
startling
arming
charming
disarming
farming
harming
rearming
reassuring