Pluto

Pluto (also known as Bruton in the 1980's version) is a fighting robot built to destroy the strongest robots in the world, including Astro. At first he wants nothing more than to furfill his duty but soon he realised that programming isn't everything and friended with Astro. He has Kokoro.

1980's series
Known as Bruton in the 1980's series dub, he was created with the sole purpose of defeating the worlds strongest robots.

He was killed by Bora, the only robot with more horsepower then him.

2003 series
Built by Shadow for the same purpose, he was made for Astro to "evolve".

He defeated the following robots:

Harley, a rocket ball player robot.

Hercules, a Greek gladiator robot.

Epsilon, an Australian female robot.

In both series he was shown to have a soft spot for uran.