Dynasty Warriors 6 (Xbox 360)

Second Costume
An officer unlocks his/her second costume upon reaching level 25.

Voice Gallery
An officer who reaches level 50 (the maximum level) will unlock his/her voice gallery.

Unlockable Difficulties
Clearing Musou mode once with any officer will unlock Expert. Clearing Musou mode with at least one officer from all factions (Wei, Wu, Shu, and Unaffiliated/Other) will unlock the ever lovable Chaos difficulty.

Movie Player
Clearing Musou mode with one of the 17 officers who are available for that mode will unlock the CG movie player.

Hint: New Officers
Want to unlock the entire officer roster? Check your mission targets. They are the key to unlocking new characters!

Hint: Achievements
You can attain the majority of the achievements by unlocking new officers (just complete mission targets on Easy or Normal) and by completing the Musou mode with each officer (on any difficulty).

There are also achievements for completing all the mission targets and clearing all the stages.

Clear Musou mode with all the available officers. Solo or co-op gaming doesn't matter, but all the officers available in Musou mode need to clear it. Also, you'll need all officers need to attain level 50. For the final achievements,you have to clear all stages - don't worry about the targets - on Chaos difficulty! Ouch...