Created as a replacement for the son of the genius scientist Dr. Tenma, Tobio, Astro is the main protagonist of the manga series. A kind hearted robot, he is still unafraid to fight when the time calls for it (and this being Astro Boy, it happens a lot). Fortunately, he has a wide array of superpowers with which to do this.
- Ass Kicks You: As having machine guns in his rear would suggest, Astro is prone to doing this from time to time.
- Badass Adorable: Being a powerful robot in the body meant to replace that of a child's, Astro is most certainly this.
- Combo Platter Powers: Has seven different powers, flight, being able to speak and understand sixty different languages, sensing if a person is good or bad, enhanced hearing, searchlight eyes, having 100,000 horsepower, and machine guns on his rear.
- Flying Brick: With two of his special powers being enhanced strength and flight, along with the durability that being a robot entails, Astro is demonstrably this trope. The amount of damage he's capable of is quite clearly seen throughout the manga.
- Lightning Bruiser: Has stated to fly at multiples of the speed of sound in the past, which only amplifies his formidable strength and durability.
- Living Lie Detector: Comes with his ability to tell whether a person is good or bad to some extent.
- Pintsized Powerhouse: Is very much this, being capable of smashing through robots many times larger than him with ease.
The Greatest Robot on Earth
Owned by a greedy sultan who built him to kill the seven strongest robots of the world, Pluto serves as the main antagonist of "The Greatest Robot on Earth". While he is not particularly malicious, he feels he has no other choice but to carry out these orders, since he was built to be the strongest.
- Affably Evil: Fairly pleasant outside of combat, and refuses to kill other robots outside of the seven he is assigned to. That being said, stunning and threatening to crush others is still fair game.
- Combat Pragmatist: Is not against attacking an enemy unawares, as Mont Blanc soon found out. He's also perfectly fine with exploiting Epsilon's love of children to defeat him, along with his need for sunlight to function at his peak.
- Fair Play Villain: Having been saved by Astro in the past, he returns the favor when he gets the upper hand in their second fight, letting him go back home. Strangely enough, he doesn't do the same for Epsilon, who also rescues him, opting to kill him after their temporary team up.
- Nothing Personal: His fights against the seven robots are all like this, doing so not out of enjoyment, but due to being created that way.
- One-Hit Kill: One of Pluto's strongest abilities, he can create a powerful electromagnetic field between his horns, destroying virtually any machinery between them.
- Redemption Equals Death: After his final fight with Astro, he does something that goes against his programming - saving the volcano they fought on from erupting, and thus killing the surrounding towns and cities. Pluto then called off his battle with Astro, losing his desire to fight. However, he is soon killed by Bora.
- Self-Destruct Mechanism: Installed into his system after his fight with Brando left him immobile at the behest of the sultan. As such, if he is defeated, he will blow up.
- Shock and Awe: Can generate electric pulses using his hands, as shown when he zaps Uran into unconsciousness. He also attempted to blast Astro with a bolt of electricity after their first fight was interrupted.
- World's Strongest Man: Attempted by the sultan, as the destruction of the seven strongest robots would leave Pluto with this title.
A Swiss mountain guide robot with 135,000 horsepower, Mont Blanc is one of the seven strongest robots on Earth, and is Pluto's first victim. Caught unawares, he is unceremoniously destroyed as soon as Pluto appears.
- An Axe to Grind: Uses one in the two pages he's seen in, to chop down trees.
- Nice Guy: Is very pleasant to Pluto, formally greeting him, before being hit with a surprise attack, and immediately destroyed afterwards.
- Underestimating Badassery: A very restrained example, revealing that he has 135,000 horsepower instead of 100,000 to Pluto. Keep in mind that Astro only had 100,000 himself, making Mont Blanc stronger than Astro.
- We Hardly Knew Ye: Lasts for a matter of two pages before being blown up by Pluto.
A month after Mont Blanc's death, North #2, another of the seven strongest robots, is targeted for destruction. Hailing from Northern Scotland, he challenged Pluto to a duel under the orders of his creator. He subsequently becomes Pluto's second victim. North #2 possessed an array of weapons and appendages which he could switch out at will, in a Swiss Army knife fashion.
- Battle Butler: Easily resembles this, with his body styled like a suit, and his deference to his creator.
- Multi-Armed and Dangerous: Possesses six large arms. He loses them all when he attempts to smash Pluto against a cliff face.
- Submissive Badass: Addresses his creator as his master, and listens to his orders to capture Pluto, all while being one of the seven strongest robots.
- Swiss Army Appendage: Once his arms are torn off, he replaces them with six new ones, consisting of drills, hammers, and pincers. This gets him killed when he grabs onto Pluto's horns.
A champion wrestling robot from Turkey, he disrupted Pluto and Astro's second fight for a chance at revenge for Mont Blanc's death. With the ability to charge at others in a cannonball fashion, he battled Pluto for much longer than the previous robots, but was also eventually destroyed, making him the third of the seven destroyed.
- Difficulty Spike: Has the dubious honor of being the first of the robots to give Pluto a challenge, potentially killing him if it weren't for outside help. All the robots after him also put up a better fight.
- Gory Discretion Shot: The only evidence of his defeat was an oil slick rising from the bottom of the ocean.
- It's Personal: Came after Pluto due to the destruction of his friend, Mont Blanc.
- Rolling Attack: Can curl up into a flying ball of destruction, tearing apart anything in his way. He destroys countless numbers of palm trees in the process of attacking Pluto.
Gerhardt is first seen visiting Astro's home before his fight with Pluto. Presenting himself as a German robot detective, he asks for Astro's help in testifying against Pluto - once Gerhardt arrests him for his destruction of three of the seven strongest robots of course. Made of a special alloy called Zeronium, he is immune to electromagnetic and thermal radiation, and thus, Pluto's deadly horn attacks. He puts up a strong fight against Pluto, but is eventually defeated, making him the fourth robot to be destroyed.
- Battle in the Rain: Gets one with his bout with Pluto.
- Chest Blaster: Has a number of these hidden underneath his clothes, which he makes full use of during his fight with Pluto.
- Explaining Your Power to the Enemy: Takes the time to tell Pluto about his immunity to thermal and electromagnetic waves before fighting.
- Half the Man He Used To Be: Is torn in two when he lands on Pluto's horns, and his usual electromagnetic pulse didn't work. Pluto just separated his horns, bringing the two halves of Gerhardt with him.
- Lantern Jaw of Justice: Has a cleft chin as part of his design, emphasising his role as a heroic inspector.
- Won't Work On Me: Repeats this almost word for word after being zapped by Pluto's electromagnetic pulses. It's soon demonstrated that he's still just as vulnerable to being torn apart.
A proud Greek robot boasting 400,000 horsepower, he fights Pluto in the Acropolis, claiming to be the most powerful robot on Earth. Possessing a special shield and spear, he openly welcomed his battle with Pluto, but soon found himself outmatched, and thus, the fifth robot destroyed.
- Blow You Away: Uses a shield which can generate powerful whirlwinds. He loses it when Pluto takes his arm.
- Detachment Combat: Overlaps with Suicide Attack. Hercules' arms and head can launch themselves as projectiles in lieu of proper weapons. Unlike most examples of this trope, this is a one use attack.
- Foil: Is one to Pluto, having similar powers (generating wind and electromagnetic pulses), and sharing a Self-Destruct Mechanism. Even their designs are almost a Palette Swap of one another. Both are also clearly designed for fighting in comparison to the other six.
- Honor Before Reason: Snaps his spear once Pluto uses it against him, leaving him weaponless, and insists on duelling Pluto one on one when Epsilon offers to team up, despite the fact that five of the seven robots fell to him.
- Let Them Die Happy: Explodes believing he defeated Pluto with his electromagnetic pulses, and thus dies the greatest robot.
- Pride: Refuses Epsilon's offer to fight Pluto together, on the grounds that he didn't want others to think he needed help defeating Pluto. He also
- Retractable Weapon: Has an extendable spear which allows him to attack targets at long distances. He snaps it in two once Pluto uses it to take off one of his arms.
- Shock and Awe: Can generate powerful electromagnetic pulses within his body, which can cause other robots to explode. However, if that fails, Hercules will explode instead.
The solar powered Australian robot Epsilon is Pluto's sixth and final victim. Caring for an orphanage and a pacifist, he is also the only other robot apart from Astro that defeats Pluto, trapping him at the bottom of the ocean, before his kind nature spares him. This proves to be his downfall, as he reveals his need for sunlight to function in the process, inspiring Pluto to fight and kill him at night time, where he was at his weakest.
- Badass Cape: Has a long, flowing one as part of his design. It gets plenty of chances to billow in the wind and underwater as well.
- Badass Pacifist: Dislikes fighting others, but proves to be more than strong enough to qualify. He's capable of lifting Pluto up with ease, using just his antenna, and putting up a fight even out of his natural element, sunlight.
- Combat Pragmatist: Believes himself to be no match for Pluto, and opts to trap him in seabed silt. Even before this, he contacts Hercules, offering to fight Pluto together to ensure his defeat.
- Enemy Mine: Temporarily teams up with Pluto to help rescue Astro, stuck at the bottom of the ocean.
- Friend to All Children: Helps run an orphanage, living with its children for ten years. He would have stayed there forever, were it not for his fight with Pluto.
- Heroic Sacrifice: Opts to save a child in the middle of his fight with Pluto, resulting in his death when this is taken advantage of.
- Light'Em Up: Is a photon powered robot, so naturally gains most of his energy from sunlight. While underneath the sun, he has near unlimited energy. He can light up the bottom of the ocean to resemble daytime, and send bolts of powerful energy that harm Pluto with his antenna.
- Save the Villain: Of his own making, but he still pulls Pluto out of a death trap at the bottom of the sea, knowing full well that Pluto would destroy him afterwards.
- What You Are in the Dark: Traps Pluto at the bottom of a deep, silt-filled ocean when they briefly team up to rescue Astro. He decides to rescue him when he hears Pluto's call for help.
- Worf Had the Flu: Pluto acknowledges Epsilon as perhaps his strongest opponent. As such, he opts to fight him on a stormy night, to prevent him from recharging his energy and using his full power. Along with this, he takes advantage of Epsilon's love for children, attacking when he's in the middle of rescuing a child.