The PlayStation 2 hardware, while legendary, simply wasn't powerful enough to handle the advanced physics and "Rage" system introduced in Tekken 6. The game was built for the , which was based on PlayStation 3 architecture.
You can find the Tekken 6 PSP ISO on archival sites like Internet Archive. Emulator: Use the PPSSPP Emulator for Android, iOS, or PC. 2. PS3 Emulation (RPCS3)
For a high-definition experience on PC, emulating the PlayStation 3 version is the best route.
