Sunstar is the final boss from Mega Man V, on the Game Boy.
He is a powerful robot that wants to dominate the entire universe and eradicate all inferior life-forms.

While being discovered by Dr.Wily at the same time as the Stardroids and being an ancient doomsday weapon from the same era as the Stardroids, Sunstar is not one of them.
When Dr.Wily activated him and tried to make him attack Mega Man, he turned on him first and then willingly attacked Mega Man.