Praise be to Allah.Praise be to Allaah.
You could take him to court. If there is a sharee’ah court there, then praise be to Allaah. Otherwise you can take to him to a court of the country in which you live, but only after exhausting all possible means of getting back what you are owed, such as getting other people to mediate in the matter.
With regard to praying against him, if it is quite clear to you that he intends to take your property wrongfully, then you have the right to pray against him.