blackmail (someone) into (something)
To coerce someone to take a certain action by threatening to expose something about them. I've known him for years and can definitely blackmail him into silence. The maid blackmailed her famous employer into paying her an exorbitant sum of money.
blackmail someone into doing something
to force a person to do something by threatening to reveal some secret about the person. Are you trying to blackmail me into doing what you want? They blackmailed me into doing it.