Baru dubeko paisa uthaune kehi upaya chha ki?

My dad lent some 4 lakhs rupees, very hard earned money, to a businessman some 10 years ago since he promised to give 24% annual interest. He kept giving the interest for first 2 years, but after that he stopped citing the problems between brothers in his family. His family is very rich and his family members' properties in Kathmandu and outside Kathmandu worth at least 25 crores rupees.

He keeps saying that he would pay the amount, but for last 8 years he has neither given the interests nor the principal amount that we lent him. It seems that his intention is not to pay back any money. What should we do?