Is Tekken 6 Compatible with PlayStation 2?

No, Tekken 6 Does Not Run on PS2

Tekken 6 was released for PlayStation 3, Xbox 360, and Microsoft Windows. It requires hardware capabilities beyond the PlayStation 2, which is an older generation console.

If you want to play Tekken on PS2, look for Tekken 5 or Tekken Tag Tournament, both of which were native PS2 releases.