Suggested by Sonic Unicron is a huge Transformer and is typically known as one of the strongest ones. It is difficult to damage him since his hull is so durable. Still, Astro Boy can do the job. He may be small, but his raw power is out of this world and his energy cannon will also deal lethal damage. As exploited in the G1 Transformers film, Unicron is often too big to do anything about smaller opponents. He has appeared in smaller versions at times, but even those wouldn’t be able to keep up with a boy who moves at atomic speeds. Astro Boy wins.