Rise of the Kasai

The Arena Champion trophy must be unlocked before you can complete all requirements of this trophy. Movies are unlocked by completing Arena challenges. Admittedly, I am not positive what the pattern is for unlocking the movies as you do not have to complete all arena challenges to unlock its movie.

There are two sub-sets of challenges for arenas: Time Attack and Body Count. You must complete all Time Attack challenges to unlock the movies so I recommend doing those first and then checking to see if the movie has been unlocked. Arena 1 unlocks Movie 1 and so on. If you have completed the Time Attack challenges and the movie has not been unlocked then move into the Body Count challenges. Make sure to complete the first challenge (defeat XXX number of enemies in XXX minutes). I had several second and third Body Count challenges that I never had to do to unlock this trophy.

The trophy will immediately unlock once all 10 movies are unlocked but you do not need to watch them.