A clean, uncorrupted backup image of the PS2 game you legally own.
The PS4's PS2 emulator has come a long way, but it's not perfect. Here's a quick look at two primary methods to run these games and what you can expect regarding compatibility: ps2 to ps4 pkg download
Players wanting to play other PS2 classics—or simply avoid repurchasing games they already owned—turned to unofficial methods. That’s where the “PS2 to PS4” toolkits emerged. A clean, uncorrupted backup image of the PS2
It's important to understand that this is not emulation in the traditional sense (like running a separate emulator application). Instead, you are essentially tricking the PS4's native PS2 emulator into launching your custom game file as if it were a legitimate, officially purchased PS2 Classic from the PSN store. ps2 to ps4 pkg download