F2P team with flying Merry, Assumes 2 CDR, and that rerolling for SPECIALS (not orbs) is allowed. This team takes 10 turns.
Stage 1: kill 5 mobs. Stall on mob. 3 Turns passed, Akainu starting CD = 17 - 2 cdr - 3 hack = 12. three turns pass, so Akainu CD for next round = 9
Stage 2: Clear normally in 2 turns. 2 turns passed, 5 turns passed total. Akainu CD for next round = 7
Stage 3: Clear normally in 1 turns. 1 turns passed, 6 turns passed total, 11 turns stalled. Akainu CD for next round = 6
Stage 4: Activate Octopus Boxer (12 turns have stalled with preemptive), clear in 2 turns. 2 turns passed, 8 turns total. Akainu CD for next round = 3
Stage 5: Preemptive = Akainu CD = 2. Activate Hack, Sabo goes from 3734k to 2987k health. Activate Boa. Hack has a red orb so deal 338k. SAbo has 2574k HP left. Now You are on turn 10. Use Kizaru to make Akainu ready. Use Akainu, MC, Kizaru, and Kuma Specials. Akainu deals 147k with his special, because it is STR type. The team's burst does 2184k, meaning after all those Sabo's HP would be 243k-- ie this is the amount of damage that MC's special needs to deal. If you reroll till MC gets that much damage, you win.