Ex and his father threatening me to ruin my Life

I was in a relationship with my ex for some years. He faked a promise of marriage to me. Later, he moved on and started seeing girls for arranged marriage. I asked him to reconsider, he refused. I informed his parents about everything, now they’re targeting me and my family.

They’re threatening to ruin my life, contacting my office and old employers, and trying to damage my reputation. I’ve suffered emotionally and mentally because of him, and now it feels like they’re plotting to destroy everything I’ve built.

What can I do legally to protect myself and stop this?