Frightening
/ˈfɹaɪtnɪŋ/
verb
To cause to feel fear; to scare; to cause to feel alarm or fright.
“Avery puts a sheet over her head, pretending to be a ghost to frighten Emily.”
adjective
Causing fear; of capable of causing fear; scary.
“Riding the rollercoaster was a frightening experience.”
Awful, terrible, very bad.