ruin your life with litigation might be illegal in some jurisdictions.
If he threatened him with a criminal threat, ie "we're going to send you to jail if you don't pay up," that I know is definitely illegal and I've heard of lawyers threatened with disbarment for it.
If he threatened him with a criminal threat, ie "we're going to send you to jail if you don't pay up," that I know is definitely illegal and I've heard of lawyers threatened with disbarment for it.