Bellamy, known by the epithet the Hyena, is a former pirate captain from the North Blue who initially appears as a brash and violent antagonist before undergoing a significant personal transformation. He is a tall, tan-skinned man with unkempt blonde hair and, in his early appearances, a distinctive, mocking grin that contributes to his hyena-like nickname. A notable scar runs across his left eye, and his body is marked with several tattoos, including a red design around his right eye on his arm. After the two-year timeskip, his appearance matures; he develops a sharper jawline, his hair is often slicked back, and he acquires additional scars on his face, reflecting the hardships he has endured.

In his first appearance in the town of Mock Town on Jaya Island, Bellamy is characterized by an arrogant, conceited, and ruthless personality. He is a firm believer in a so-called New Age, a philosophy that dismisses the romantic dreams of adventure and treasure, such as the search for the One Piece or the legendary Sky Island, as foolish fantasies of a bygone era. He operates on a cynical and materialistic principle that only tangible strength and immediate wealth matter, and he openly mocks and attacks anyone who espouses grand dreams. His cruelty is on full display when he assaults a fellow pirate over a card game and later savagely beats the explorer Montblanc Cricket to steal his gold. Bellamy is also a coward who prefers to pick fights he believes he can win, a trait that makes his eventual defeat all the more humbling.

Bellamy's primary motivation throughout much of the story is his deep-seated and desperate desire for approval from the Warlord of the Sea, Donquixote Doflamingo. Since childhood, he has idolized Doflamingo and views him as the epitome of a powerful and successful pirate. This obsession drives him to adopt Doflamingo's flag as his own and to strive relentlessly to become an official high-ranking officer of the Donquixote Pirates. His role in the story is that of a foil to Monkey D. Luffy. On Jaya, Bellamy represents the cynical and practical worldview that directly clashes with Luffy’s unwavering idealism and pursuit of his dreams. Their conflict is not just physical but ideological, and Luffy's one-punch victory over Bellamy serves as a powerful narrative statement that dreams are not a weakness.

His key relationships are the central forces that shape his character arc. His relationship with Luffy begins with contempt and mockery but evolves into one of grudging respect and eventual friendship. After being defeated, Bellamy is haunted by the question of why a dreamer like Luffy possessed such overwhelming strength. This leads him to undertake a dangerous journey to a Sky Island himself, seeking to understand what Luffy already knew. When they meet again two years later in the Colosseum of Dressrosa, Bellamy is a changed man; he no longer laughs at dreams and treats Luffy with a newfound respect, even as he remains trapped by his loyalty to Doflamingo. His relationship with Doflamingo is tragically one-sided. Bellamy offers fanatical loyalty, but Doflamingo sees him as a disposable pawn, useful only for his ambition. The climax of Bellamy's character development occurs when he realizes that Doflamingo never intended to accept him and has been manipulating him all along, a betrayal that shatters his lifelong idolatry.

Over the course of the series, Bellamy undergoes one of the more dramatic developments. He transforms from a small-time, bullying thug into a man of principle and surprising honor. Despite being ordered to kill Luffy by Doflamingo and facing certain death himself, Bellamy refuses to betray his own code or the man he once chose to respect. He would rather die than be seen as a turncoat. This loyalty, even to an undeserving master, demonstrates a perverse but powerful sense of integrity. After being freed from Doflamingo's control and saved by Luffy, Bellamy finally abandons his old ambitions. He humbly requests a piece of Luffy's Vivre Card, a gesture of profound respect and friendship, before retiring from piracy entirely.

In terms of abilities, Bellamy is a Paramecia-type Devil Fruit user who ate the Bane Bane no Mi, or Spring-Spring Fruit. This power allows him to transform any part of his body into a steel spring, granting him tremendous agility, speed, and striking power. He can compress his limbs to store immense kinetic energy and release it in devastating attacks. His signature techniques include Spring Snipe, where he launches his leg like a projectile, and Spring Hopper, where he bounces at incredible speeds between surfaces to deliver a powerful, unpredictable charge. After the timeskip, he develops more advanced techniques like the Spring Death Knock, a compressed punch of tremendous force. He also demonstrates the ability to use Armament Haki, coating his attacks in a black, armor-like enhancement to increase their defensive and offensive capabilities. Following his retirement, he leaves behind his life as a brawler and becomes an apprentice fabric dyer, finding a peaceful and productive life far removed from the violent world of piracy.