After unlocking every character, save the ones unlocked through the true ending(Orochi, Orochi X, Sun Wukong, Taira no Kiyomori, Susanoo and Ne Zha) you then need to replay the chapter four stage ''Yuan Lu Ji Tometsu-sen''.
This in turn unlocks the final two stages, clearing these two unlocks the ''True Ending''
Get all the characters that aren't Susanoo, Nezha, Kiyomori, Dodomeki, Gyuji, Orochi, Orochi X. That would involve pretty much completing every circle mission at the bottom of them mission selection screen and every redux mission too. And then there's Lu Bu.
Team Fortress 2 Autobalance: "You are now on the LOSING TEAM!!"