awful
dire
direful
dread
dreaded
dreadful
fearful
fearsome
frightening
horrendous
horrific
terrible
causing fear or dread or terror
the awful war
an awful risk
dire news
a career or vengeance so direful that London was shocked
the dread presence of the headmaster
polio is no longer the dreaded disease it once was
a dreadful storm
a fearful howling
horrendous explosions shook the city
a terrible curse