Just a little addition to make here: if you, like me, didn't get the cheevo to pop the first time around, for whatever reason, exit the game completely and start it back up. Replay the stage without turning off the system or allowing it to sleep. For reference, I played it on hard using a maxed out Zhang Liao. It popped during the battle results screens. This seems to work for all of the stage completion achievements so far, as I didn't get any of them the first time around.