I'll knock your block/head off! informal
Used to threaten someone that you will hit them, usually in the head
Say that again and I’ll knock your head off!
The boxer said that he will knock the opponent's head off.
The cops arrested him after he threatened to knock their blocks off.
To threaten that you will punish someone severely because of what they have done
I'm not stupid or easily scared.
Are you informing me of good or bad news?
To use force or threats to get someone to do what you want.