Unlock Secret Characters:

To play as some of the secret characters complete the game a certain amount of times to unlock it

Tekken Ball mode:

Complete the game with all the regular characters

Unlock Gon:

Beat him in Tekken Ball mode

Unlock Dr. B:

Complete Tekken Force mode 3 times collecting the 3keys then play Tekken Force one more time and beat Dr. B at the end to unlock him (be careful he is very hard)

Tekken Theatre:

Beat the game with all the characters (except D.r B)