Renaming the original steam_api64.dll to something like steam_api64_o.dll and replacing it with a modified DLL that "proxies" calls to the original while injecting DLC ownership data.
New York (The Bank), Hantu Port (Sniper), Special Assignments hitman 2 dlc unlocker full
Q: What is Hitman 2 DLC Unlocker Full? A: Hitman 2 DLC Unlocker Full is a tool that allows players to unlock all the DLC content in Hitman 2. Renaming the original steam_api64