Changes own slot to DEX and deals varying amounts of DEX damage (more when HP is low) to a single enemy The exact multiplier used to compute the damage is proportional to the crew's remaining HP and is higher the lower the HP is. The multiplier is calculated as: 50 * ( 1 - (remaining HP) / (total HP) )
Ok but not great stats, difficult to socket. His CA was good for speed running through some evolvers, but now generally people use Baccarat Gran Tesoro Concierge rather than worry about saving some time - and you can get all the speed you need from Dreadnaught Sabre anyway. His special effectively deals 50 x your remaining HP, which is in the end not that much, and rarely needed.
50 x your HP means, let's say with Moby Dick or such, 50x20k=1m damage. Not bad, but it does require some serious thought. First, you want to ideally get your HP down as much as possible, ideally to 1. You can get this through health-reducing units (list). Or you can just tank some hits from enemies, but that requires more skill and luck. Next, you want to maximize the amount of damage dealt. There are two ways of going about it. First, run a DEX team with Kaku CP9’s Strongest. Second, run an HP boosting captain - Usopp Hero Fighter of the Forest may be the best one there is. In either case, you'll want Moby Dick or such. Such a team has potential to deal 2-4m damage to all enemies, and that could be useful for some battles.