Killua Zoldyck, raised within the infamous Zoldyck Family of assassins, endured brutal training from infancy to forge him into a peerless killer. His childhood intertwined torture to immunize him against pain, poisons, and electrocution, alongside relentless drills in stealth, martial arts, and assassination. By six, he entered Heavens Arena, ascending to the 199th floor in two years. Though groomed as heir, he shattered expectations, attacking kin and fleeing to pursue the Hunter Exam for independence. The Hunter Exam ignited a transformative bond with Gon Freecss, reshaping Killua’s trajectory. Their friendship anchored his quest to carve an identity beyond his lineage, clashing with a childhood marred by manipulation—most notably Illumi’s Nen needle embedded in his skull to enforce cowardice. This psychological shackle forced retreats from peril until Killua ripped it free during the Chimera Ant crisis, defying Illumi’s dominion. A Transmuter, Killua wields Nen to morph aura into electricity, crafting techniques like Godspeed for lightning-fast reflexes and Thunderbolt for explosive strikes. Childhood punishments granted immunity to currents, enabling these powers. His physical feats include prying open 64-ton Testing Gates and outmaneuvering elite fighters undetected. His path intertwined with Gon’s search for Ging, honing Nen in Greed Island and battling Chimera Ants. When Gon’s life hung in the balance, Killua prioritized saving him over family edicts, leveraging his sister Alluka’s reality-warping entity, Nanika—defying Zoldyck restrictions and clashing with Illumi to safeguard his friend. Spin-offs expanded his exploits: reclaiming stolen relics and defending Heavens Arena in *The Last Mission*, showcasing tactical ingenuity alongside allies. Post-Chimera Ant, he parted with Gon, choosing to roam with Alluka, shielding her from familial exploitation. This shift underscored his rejection of dynastic duty, treating Alluka and Nanika as distinct beings worthy of dignity. Killua’s evolution bridged lethal conditioning and emerging morality, often risking himself for others. His defiance of psychological coercion and physical extremes, paired with strategic brilliance, framed a figure driven by loyalty and the relentless pursuit of self-determination.