Eustass "Captain" Kid is the leader of the Kid Pirates and a member of the Worst Generation. He made his debut in the series alongside the rest of the Supernovas in the Sabaody Archipelago arc. From the get-go, Kid impressed One Piece fans with his imposing figure and a different perspective. Kid did not see much action in One Piece until the focus shifted to the Land of Wano.
In the Wano Country arc, it was revealed that Apoo had betrayed the alliance, which caused Kid and Killer to end up in a perilous position. The two Worst Generation members were tortured by the members of the Beasts Pirates, but their spirits didn't break. Even after the arc ended, fans did not get an opportunity to see the backstory of Kid and his crew. However, that changed after the release of the most recent SBS.
The Untamable Island
Eustass Kid was born on an unnamed island in South Blue. The island was not affiliated with the World Government, meaning it was a lawless place. The island was ruled over by a criminal gang, and due to the absence of any royalty, they took control. The place was divided into four districts, and each one was under the rule of a local gang. The leaders of these gangs were: Eustass Kid, Killer, Heat, and Wire. Despite the animosity between the gangs, Kid and Killer were extremely close friends.
At some point, the two of them became acquainted with a girl named Victoria Shirton Doruyanaika, and soon enough, they became very close friends. According to Oda's statement in an SBS, Killer, and Kid had a crush on Victoria. Oda did not elaborate on whether Victoria had any kind of feelings toward either of them, so that part remains a mystery. Things between the friends were going fine until one day, the ruling criminal gang of their country murdered Victoria, which made Kid furious.
Launching A Coup d'etat
Kid was outraged by the death of his close friend, and he wanted to avenge her. So, he united all the four gangs and led a coup d'etat against the criminal group that killed Victoria. Kid, Killer, Heat, and Wire were successful in their endeavor. They crushed their enemies, and liberated the country from their rule. After the event, Kid stated that he no longer desired to live in such a confined place, and this led to the formation of the Kid Pirates.
As a tribute to their late friend, Victoria, Kid named his shop Victoria Punk. The Kid Pirates made quite a name for themselves and the World Government placed high bounties on their heads. After leaving Sabaody, the Kid Pirates were involved in two main incidents. They fought against the Red Hair Pirates, which ended in a bitter defeat for them. The biggest moment of the crew was attacking one of the Sweet Commanders of the Big Mom Pirates.
Role In Wano
The Kid Pirates were heavily involved in the Wano Country arc as they sought revenge against Kaido for what he had done to Killer and Kid. The crew allied with the Straw Hat Pirates and the Heart Pirates as they marched on to take down Kaido and Big Mom. Kid and Killer were involved in the fight on the rooftop, but they couldn't do much against the two Yonko. The alliance formulated a plan to separate the two monsters and take them down separately.
Law and Kid fought against Big Mom, and it took a lot of effort to take her down. Kid's devil fruit awakening allowed him to help Law out in their fight, and before long, the Worst Generation managed to do the unthinkable and defeat Big Mom. Meanwhile, Killer was fighting Basil Hawkins, who was also a member of the Worst Generation in the service of Kaido. It wasn't an easy job to defeat Hawkins, but Killer did not give up. He kept fighting until he found a way to hurt Hawkins, and finally defeat him.
Post-War and New Bounties
It didn't take long for the news about the Worst Generation's exploits in Wano to spread throughout the world. It caused the World Government to increase the bounty of the people involved in the action. Eustass Kid, Trafalgar Law, and Monkey D. Luffy all received a bounty of 3,000,000,000 berries. The bounties of Kid's crewmates remain unknown, but that might change in the future arcs. With the war over, the alliance had served its purpose, so it disbanded.
All three pirate crews went their separate ways. The Straw Hats are on Egghead Island, while the Heart Pirates are engaged in a fight with the Blackbeard Pirates on Winner Island. The location of the Kid Pirates remains unknown, but it is possible that they headed to the place where they can find the "man with the burn scars." Kid mentioned that they already have a lead, so it would make sense if they headed in the same direction. Kid has stated that he wants to become the Pirate King, so he wouldn't want to fall behind his fellow Worst Generation members, and given that he has two Road Poneglyphs already, he is not that far from his goal. The backstory of Eustass Kid and his crewmates helped to shed light on their behavior. Considering Kid is from a lawless place, it is not surprising why he's so violent. It will be interesting to see if the anime ever adapts this information and gives the fans a couple of episodes about Kid.