What he does

He 10 Million health and deals 19k damage on normal attack.
He pre-emptively changes his type from STR to INT and shuffles your orbs.
He has a defense reduce debuff protection
Every 2 turns he removes all your buffs and debuffs dealt to him and shuffles your orbs. With a chance of getting BLOCK orbs.
After defeat he revives for 20% of his HP(around 2 million+ health), cuts your HP by 80%, paralyzes your team for 3 turns and silences special of a QCK unit on your team(if you have one)
After he revives he also gives himself Damage immunity buff from all types (STR, DEX, QCK, PSY and INT) for two turns.
After he revives he attacks normally for two turns and on the third turn does his big damage of 500,000

Team :

Lucy / Lucy

Diamante / Doffy

Usopp 6+ / Lucy

1-4: Stall on the turtle and kill everything else in time.

Garp 1: On entering use Colo Lucy, Lucy and hit at least 4 perfects => 4,376k dmg + 2,000k dmg

Garp 2: Doffy & kill him => 4,036k dmg

Garp 3: Use Diamante

Garp 4: Nothing

Garp 5: Use Usopp & farm orbs

Garp 6: Use 2nd Lucy and kill him again