From TV Animation: One Piece Grand Battle! 2 Hints & Cheats

Unlockables

To get these characters, you must first unlock Crocodile, then play Event Battle with certain characters and beat them at the boss battle.

Unlockable	How to Unlock
play as Tashigi	Alvida
play as Mr. 3	Kreig
play as Waporu	Kuro
play as Smoker	Buggy
play as Crocodile	Arlong
play as Mr. 2 Bon Clay	Pandaman
After you have unlocked Alvida, Kreig, Kuro, Buggy, Arlong, Pandaman, play Event battle with Luffy. Fight and defeat Shanks at the boss battle and you could now use him in event battle and grand battle.	Shanks
Use any character on event battle on normal mode and without using continue, your 5th battle event will be ka-ru the bird.	Ka-ru
Go to training stage and choose a character.Pick the metal anchor and throw it up.Go below the anchor and simply press X(defend) button when the anchor reach your character.Do this untill the combo defending it reach 100.	training stage at versus battle
After you have unlocked Alvida, Kreig, Kuro, Buggy, Arlong, Pandaman, play Event battle with Zoro. Fight and defeat Mihawk at the boss battle and you could now use him in event battle and grand battle.	Mihawk
Complete the training mode by doing all of the character's attacks from the move list.	Extra Hard Difficulty
Unlock all characters except Ace, then beat story mode with all characters, then beat it again with Smoker on hard difficulty, then beat Ace in the last battle.	Ace
Beat story mode with Ace on any difficulty.	BGM Test
Beat Event Mode With Nico Robin(Miss All Sunday) On Any Level Of Difficulty	Mr.0 Crocodile

Unlock Event Battle Statistics
Do all of the characters attacks in training. Then you can see that characters statistics in Event Mode by going to the Character Biography section (The red treasure box), and going to the second page of the third section (from top). The first one is the number of times you've done the event mode for the character, and the second one is the number of battles done in the event mode with that character
Alternate Costumes
Clear the event battle once with the characters that you want to select the alternate costumes.Then select the characters in event battle or versus battle and press R1+circle or L1+circle or L1+R1+circle.There is three alternate costumes.Some characters only have one or two alternate costumes.