Make all your slots red during Chapter 1 "Encounter! Alvida Pirates". You will need 6 characters in your crew, including a Friend or Helper Captain.
Take with you characters with low ATK like Treasure Turtles and shuffle orbs, attacking the enemy, until they are all red. You can also choose to take some orb manipulators with low ATK like Cabin Boys, but you have to take turns to load specials.
From Alvida's Hideout, recruit a total of 30 of Alvida's crewmembers: any combination of STRFighters, DEXSlashers, QCKStrikers, STRShooters, and Cannoneers. All recruited crewmembers must be Cabin Boys.
Clear Alvida's Hideout chapters until you get a total 30 Cabin Boys. You can check which characters you need Here, it's not necessary holding characters in the Character Box to clear the mission.
Deal a cumulative total of 400.000 damage or more during Chapter 3 "Showdown!! Iron Mace Alvida" using only normal attacks. There are no restrictions on characters or number for on Captain, Friend, and crew.
Enemies are very weak so you need low ATK but high damage boost chain like Monkey D. Luffy Gear Third. Teams suggested:
Use recruited Alvida Pirate crewmembers to beat Chapter 3 "Showdown!! Iron Mace Alvida". Your Friend or Helper Captain must be a Cannoneer Cabin Boy. The crew must have a STR Fighter, DEX Slasher, QCK Striker, STR Shooter, and Cannoneer. All crewmembers must be Cabin Boys.
Make this crew: Helper Captain or Friend Your Crew
Beat Chapter 3 "Showdown!! Iron Mace Alvida" with 15 taps or less.
Use high damage characters that can one-shot enemies without finishing the attack. This will allow you to kill only a few units per turn while stalling for specials. Bring with you 1 or more characters with a low cooldown skill that attack all enemies like Butchie and unleash them on the final round. The special will not count as one of your taps.
Another method is to use Monet Donquixote Pirates or other post turn damage dealers as Captain or Friend/Helper Captain, as the post turn damage doesn't count as a tap. You can effectively complete this task with as little as seven taps.