What are the top private spy companies in the world?

It's difficult to determine the top private spy companies in the world as the industry is largely secretive and not regulated. However, some of the well-known private intelligence and security firms include:

1. Blackwater (now known as Academi)
2. G4S
3. Control Risks Group
4. Pinkerton
5. Kroll Inc.
6. Global Risk Strategies
7. Erinys International
8. Mant affinity Intelligence
9. International Intelligence Limited
10. Diligence LLC

It is important to note that some of these companies have faced controversy and legal issues related to their practices. Additionally, the information provided by these companies should be carefully evaluated, as they may have biases and conflicts of interest.