Auron’s Overdrive is called Bushido and it requires that you enter a sequence of buttons within a given time limit to successfully perform the move. The faster you enter the pattern of buttons the more damage the Overdrive will do.
There are four moves which can be performed when using Bushido - Dragon Fang, Shooting Star, Banishing Blade and Tornado. More information about each can be found below:
You receive Dragon Fang at the beginning of the game. It hits all enemies and can delay their turn if the button sequence is successfully inputted.
You receive Shooting Star automatically after you defeat Spherimorph in Macalania Woods. Using the move will cause damage to one enemy and, if you successfully complete the button sequence, has the potential to eject an enemy from battle. Bosses cannot be ejected from battle.
You receive Banishing Blade after you find and view three Jecht Spheres. Check out the Jecht Spheres section (by clicking on the link) for a list of Jecht Spheres and where to find them throughout Spira. It hits a single enemy. Successfully completing the button sequence will cause the Full Break status effect.
You receive Tornado after you find and view all ten Jecht Spheres. Check out the Jecht Spheres section (by clicking on the link) for a list of Jecht Spheres and where to find them throughout Spira. It hits all enemies for a ton of damage. Successfully completing the button sequence will cause additional damage.