Here is the full list of all 14 Grand Guilds achievements.
Finish the main story.
Gather all of Wentz's journal entires.
Unlock the 9th character.
Get a character to level 40.
Unlock the 7th character.
Unlock the 8th character.
Unlock the 3rd character.
Unlock the 4th character.
Unlock the 5th character.
Unlock the 6th character.
Obtain your 1st legendary card.
Complete all three parts of the Mysterious Pieces questline.
Unlock the 2nd character.
Win your first battle.