How do you unlock devil kazuya on tekken 4 ps2?

If you are referring to Devil Jin, you must either a) complete the "Devil Within" game mode, or b) complete at least 200 matches in either Story Mode or Arcade Mode.

PS. For future reference, please place your questions in the appropriate category. For example, this is a question about Tekken 5, which has no relevance whatsoever to Guitar Hero, which is the category you placed this question in.