Alvida

"Iron Mace" Alvida is the former captain of the Alvida Pirates and the first antagonist encountered by Luffy in the anime present timeline (in the manga, Higuma was the first villain). Due to her actions, she can be regarded as the secondary antagonist of the Romance Dawn Arc and the tertiary antagonist of the Loguetown Arc.

After her defeat against Luffy, she allies with Buggy and becomes one of the two captains of the Buggy and Alvida Alliance. She was the acting captain of the crew during Buggy's time in Impel Down and during the Battle of Marineford. After reuniting with Buggy, his army of Impel Down Convicts, and Galdino (and with the addition of Buggy becoming a Warlord of the Sea), her alliance with him has evolved into the Underworld Organization known as Buggy's Delivery

Abilities and Powers
Initially, Alvida was only mildly formidable by East Blue standards. Though large and strong enough to captain her own crew and earn a minor bounty, she was quickly outfought and knocked unconscious by Luffy. She successfully landed only one blow, which was rendered completely ineffective by Luffy's rubber body and the angling of the spikes on her mace. Her intellect was also unremarkable and easily overtaken by her temper and vanity.

Following her defeat by Luffy, she became noticeably more resourceful and judicious. With apparently no extrinsic help, she was able to navigate the East Blue and secure an alliance with Buggy, her coolheaded prudence counterbalancing his easily-excited crewmen.

Devil Fruit

 * Further information: Sube Sube no Mi

Alvida ate the Sube Sube no Mi, a Paramecia-class Devil Fruit that grants her the ability to harmlessly "slide" virtually any physical attack off her skin. This also allows her to "skate" along level surfaces on her bare feet, though she apparently requires a ramp to build up initial momentum.

In addition, the Sube Sube no Mi drastically changed her physique, eliminating her previous bulk and making her beautiful enough to charm whole crowds of men on sight. This new physique has apparently not affected any of her physical prowess, as she is still strong enough to wield her Iron Mace with ease.

Weapons
Alvida's trademark weapon is a heavy, spiked Iron Mace (金棒 Kanabō?, "Iron Club" in the English versions), which can easily maim or kill an ordinary man in one swing. She can also throw it with enough accuracy - at least from short distances - to shatter an entire wooden shack.

In addition to the mace, she also carries at least one flintlock pistol at all times, and was skilled enough to drive off a giant crab with one shot.