Aokiji:
Clear event battle with Luffy, Zoro, Nami, Usopp, Sanji, Chopper, Robin, Buggy, Kuro, Krieg, Arlong, Smoker, Bon Clay, Crocodile, and Foxy. Then, play event battle again with Luffy. In the final stage you will battle Aokiji. To unlock Aokiji you must use your level 2 special.

Arlong:
Clear event battle with Nami.

Bon Clay:
Clear event battle with Chopper.

Buggy:
Clear event battle with Zoro.

Crocodile:
Clear event battle with Robin.
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Don Crick:
Clear event battle with Sanji under the normal difficulty setting.

Enel:
After clearing event battle with Luffy, Zoro, Nami, Usopp, Sanji, Chopper, and Robin, complete their move list in training mode. A picture should flash by of Enel challenging you. Then, play a regular tournament at Grand Tours (tournament mode). One of the character will be replaced with Enel. Defeat and win the tournament.

Foxy:
Clear event battle with Chopper twice.

Krieg:
Clear event battle with Sanji.

Kuro:
Clear event battle with Usopp.

Mihawk:
Clear event battle with Zoro under the very hard difficulty setting after Shanks has been unlocked unlocked. Defeat mihawk with a level 2 special after getting hit with Mihawk's level 2 special to unlock him.
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Shanks:
Clear event battle with Luffy under the very hard difficulty setting after unlocking Aokiji and Enel.

Smoker:
Clear event battle with Luffy.
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Very hard mode:
Clear hard mode in event battle with more than ten characters.
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Alternate title screen:
Unlock all the characters to get a new title screen that features everyone.
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Alternate costumes for The Straw Hats:
After unlocking Shanks and Mihawk, complete the entire move set for all The Straw Hat Pirates in training mode to unlock a third costume for them inspired by the Color Walk books.
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After unlocking the third Straw Hat costumes, complete Grand Battle thirty times or Event Battle six times, with each of the Straw Hat crew to unlock a fourth alternate costume.

Marine HQ stage:
After unlocking everyone, complete their move lists in training mode. After doing so, destroy all the pillars in the stage. Do this with every character to unlock the stage.
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Maxim stage:
Clear event battle with Enel.
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Davy Back Fight mini-game unlockables:
By winning the Davy Back Fight min-game the indicated amount of times to unlock the corresponding bonus.
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Breaking Krieg's Armor: 29 times
Crash Rush Boxer (the box breaking): 18 times
Donut Race: 10 times
Groggy Ring: 4 times
Sanji & Zoro voice (announcing): 33 times; also need all support character voices unlocked
Snow (getting rid of snow): 26 times
The "Fix" sign: 34 times

Play data:
Clear Event battle under very hard difficulty to view the stats for your battle.

Ending movies:
Clear Event battle to unlock the ending movie at the "Theater" menu.

Gallery:
Clear Event battle to unlock that character's images in the gallery.

Voice collection:
Clear Event battle to unlock that character's voice collection at the "Treasures" menu.

BMG select:
Clear Event Mode with Mihawk under hard difficulty setting to unlock the "BMG Select" at the "Treasures" menu.