Piccolo is a Namekian warrior who first appears as a dangerous antagonist before gradually becoming one of the most dependable members of the heroes' side. He is the reincarnation of King Piccolo, the demonic tyrant who once terrorized the Earth, and he was born with the memories and ambitions of his predecessor. His earliest goal is to avenge King Piccolo's death at the hands of Goku and to fulfill the old demon king's dream of conquering the world. After being narrowly defeated by Goku at the World Martial Arts Tournament, Piccolo spends the following years training in isolation, still nursing his hatred and his plans for revenge.

Piccolo's personality in his early appearances is cold, calculating, arrogant, and ruthless. He shows no mercy toward his opponents and treats others as disposable tools. As the story progresses, however, his character becomes more complex. He is a solitary figure who prefers to keep his distance from others, and he speaks little outside of combat, yet he is also a brilliant tactician with a sharp, analytical mind. He remains stoic and calm even under extreme pressure, and his harsh demeanor slowly gives way to a quieter sense of responsibility and care. His pivotal change begins when he takes Son Gohan, the young son of Goku, into the wilderness to train him for the coming battle against the Saiyans. During that time, Piccolo develops a genuine attachment to the boy, and that relationship softens him in ways that his former self never could have experienced.

Piccolo's motivations shift dramatically over the course of his arc. Initially driven by vengeance and a desire for domination, he becomes motivated instead by survival, by the need to protect the Earth, and, most importantly, by his devotion to Gohan. His alliance with Goku against the Saiyan Raditz marks the beginning of his turn away from villainy. It is Piccolo who delivers the fatal blow that kills Raditz, a moment that also costs Goku his life, although Goku had willingly sacrificed himself to make the attack possible. Piccolo then takes responsibility for preparing Gohan for the arrival of the other Saiyans, and during the battle against the Saiyan warrior Nappa, he throws himself in front of an attack to save Gohan and dies. His death, alongside the death of Kami, the guardian of Earth, shows how far he has come from the revenge-driven demon he once was.

After being revived on the planet Namek, Piccolo's role in the story expands. He fuses with Nail, a wounded Namekian warrior, gaining a significant increase in power and knowledge, and he battles against Frieza alongside the other heroes. Later, he fuses with Kami, his good counterpart, reuniting the being that originally split into the evil King Piccolo and the benevolent guardian. This fusion removes the last traces of malice from him and makes him a completely good-hearted warrior, while also greatly increasing his strength. He continues to serve as a key strategist and fighter during the conflict with the artificial being Cell, training Gohan in the Hyperbolic Time Chamber and helping to prepare the younger generation for the threats to come.

Among his key relationships, the bond with Gohan is the most important. Piccolo begins as a harsh and demanding trainer but becomes a devoted protector and, in many ways, a second parent figure to the boy. His relationship with Goku transforms from bitter rivalry into mutual respect and friendship, as the two come to trust each other as comrades. His connection to Namekian culture also runs through his story, expressed through his fusions with Nail and Kami and through his role as a mentor to Dende. He remains somewhat apart from the larger group, yet his actions consistently show that he genuinely cares about the people he once considered enemies.

Piccolo possesses a wide range of abilities rooted in his Namekian physiology. He can regenerate lost limbs and recover from serious injuries as long as his head remains intact, and he can stretch and extend his arms for long-range attacks. He has superhuman strength, speed, and hearing, and he is capable of flight and of moving so quickly that he becomes invisible to normal eyes. He is highly skilled in energy manipulation, with his signature technique being the Special Beam Cannon, a piercing energy attack that he used to kill Raditz. He also uses other energy blasts, can create a giant form by greatly enlarging his body, and can communicate telepathically. Most notably, as a Namekian of the Dragon Clan, he is connected to the creation of the Dragon Balls, the wish-granting relics that play a central role in the world he protects. Through his experiences, his sacrifices, and his relationships, Piccolo develops from a vengeance-driven demon into a wise, powerful, and protective warrior whose loyalty to his friends becomes one of his defining traits.