frightening
She's a scary woman.
I've always found him a bit scary.
When you think how much power these people have, it's scary.
She'd had a dream in which scary monsters were chasing her.
I really thought I was going to fall - it was a scary moment.

SMART Vocabulary: related words and phrases

Describing things that cause fear
awesome
awesomely
awesomeness
bloodcurdling
chilling
fearsome
fearsomely
frightening
frighteningly
greasily
imposingly
intimidating
intimidatingly
scarifying
scarifyingly
spooky
terrifying
terrifyingly
traumatic
traumatically

scary | American Dictionary

scary
adjective[ -er/-est only ]
us/ˈskeər·i/
making you feel frightened:
The idea of surgery was very scary to me.