intimidate, threaten

(おどす) The normal word for threaten.   $$$
かす(おどかす) To intimidate. 脅かす doesn’t really sound like a literal “Do this or else I’ll break your legs!” type of verbal threat. If a big enough guy shows up at your house at 3AM, he doesn’t need to put it into words.
(きょうはく) More formal. Not just to threaten, but to be intimidating.
(きょうかつ) The legal term for blackmail or extortion.