Pluto

Pluto (プルートウ, Purūtō) is the central antagonist of the iconic The Greatest Robot in the World (地上最大のロボット, Chijō Saidai no Robotto) story arc. His creation was commissioned by the corrupt sultan Chochi Chochi Ababa III to become the "strongest robot in the world" by killing all his competition in this field. These victims include Montblanc, North #2, Brando, Gesicht, Hercules, and Photar, all of whom he destroys with ease, demonstrating himself as an emotionless killing machine, blindly loyal to his master and caring for nothing besides fighting. When fighting Astro Boy, his final target, Pluto begins to question his actions after being saved by his enemy. He also develops a soft spot for Astro Boy's sister, Uran. During their final battle at a volcano, Pluto's creator reveals an even stronger robot named Bora, and Pluto sacrifices himself to destroy this enemy, save Astro, and contain the volcanic eruption.