ULPT: I want to ruin someone’s life

I want to ruin someone’s life. My dad had a business with his step brother and had no names on any documents when they first bought it as my dad had no status. But after my dad became a citizens the stepbrother refused to add my dad’s name. He then sold the business without telling my dad and blackmailed him to work for him or he will take all the money. This is just the tip of the ice berg as to what a piece of shit he is. He has stolen thousands from my dad and taken advantage of him over and over. How do I legally ruin his life?