Eustass Kid is the captain of the Kid Pirates. He was introduced as one of the Worst Generation and the Eleven Supernovas, possessing the highest bounty amongst them at the time due to his vicious and aggressive nature. He possesses the abilities of the devil fruit Jiki Jiki No Mi.
Eustass Kid was first seen during the Sabaody Arc, where the Eleven Supernovas were present. While initially viewing Monkey D. Luffy and Trafalgar Law with disdain, he eventually teamed up with them to face off against the Marines. After defeating the wave of Marines, he then bid farewell to Luffy and tried to make an escape, but was confronted by a Pacifista. He was then forced to ally with Law and the Heart Pirates to fight against it.
During the Timeskip
Kid was said to have instigated multiple conflicts through the timeskip, even challenging the Red Hair Pirates. It resulted in a crushing defeat and the loss of his left arm. He also attacked a commander of Big Mom and stole a poneglyph before fleeing.
During the Dressrosa Arc, he was shown to be instigating a fight against an Emperor once more, this time against Kaido. He teamed up with Killer and Hawkins, but were utterly defeated and imprisoned.
After Luffy was defeated and thrown in prison as well, they reunited once more. Over their time inside, they constantly competed over doing prison work and eventually became reluctant allies. After escaping from prison and several skirmishes, Kid joined fellow Supernovas Luffy, Zoro, Law, and Killer on the roof to battle against the allied Emperors Kaido and Big Mom.
The Supernovas agreed that they had to split up the two Emperors to stand a chance at winning. Kid and Law ended up facing off against Big Mom, and only managed to defeat her after a lengthy battle and using their awakened Devil Fruit abilities.
At the end of the arc, Kid parted ways with Luffy and Law, and set sail for Elbaf Island.
Egghead Island Arc
During the Egghead Island Arc, Eustass Kid challenged the Red Hair Pirates once again at Elbaf. After Kid refused to surrender his road poneglyphs, they decided to start the battle. However, after Shanks saw into the future the damage Kid would do to his allies due to the latter's increase in power, he decided to take action himself this time and defeated Kid and Killer with a single strike - while Dorry and Broggy destroyed their ship. This resulted in their second crippling defeat at the hands of the Red Hair Pirates. With him and his crew left sunken in the sea, their current status is left unknown.
Eustass Kid has been shown to be incredibly aggressive, vicious, and violent in nature. It allowed him to garner a bounty of 315,000,000 - which was the highest amongst the Eleven Supernovas at the time. He is also reckless and fearless, being willing to challenge and fight anyone - including three of the four original Emperors. He can also be somewhat childish at times, being easily taunted and extremely competitive over trivial matters.
Abilities & Powers
Eustass Kid was introduced as one of the most powerful pirates of the Worst Generation, being able to showcase a power level equivalent to Monkey D. Luffy and Trafalgar Law during the Sabaody Arc. He has eaten the Devil Fruit Jiki Jiki No Mi, which has given him magnetic powers - allowing him to not only attract and repel metallic objects, but also form powerful weapons with it. He was also one of the key players in taking down Kaido and Big Mom, allowing him to gain his current bounty of 3 billion berries, making him recognized as one of the most dangerous pirates in the world.
Haoshoku Haki: According to Kaido, Kid possesses the ability to use Haoshoku Haki. However, he has not showcased any usage of it.
Busoshoku Haki: Kid is confirmed to possess the ability to use Busoshoku Haki.
Kenbunshoku Haki: Kid has shown the ability to use Kenbunshoku Haki, as seen during the Wano arc where he sensed Luffy's defeat at the hands of Kaido as well as Luffy's awakening of his Devil Fruit.