Collocations for frightening - adj.

be, feel, look, seem, sound | become, get
The situation was getting quite frightening.

make sth
What can we do to make the experience less frightening?

find sth
He found the responsibility rather frightening.

extremely, genuinely, positively, really, truly, very | almost | a bit, fairly, a little, pretty, quite, rather

for
This is extremely frightening for elderly people.

to
It was all very frightening to a small boy.