Bass

Bass, also known as Forte (フォルテForute) in Japan, is a Robot Master created by Dr. Wily to imitate Mega Man's design, along with Treble, an imitation of Rush's design. He was created based on a research conducted on Mega Man with the intention of surpassing his power sometime during or before the events of Mega Man 6, and made his debut in Mega Man 7 Mega Man classic series, his goal is to defeat Mega Man and become the most powerful being in existence. Although Bass and Mega Man are rivals, at times they team up to take down mutual enemies of the two. Despite being created by Dr. Wily, Bass frequently rebels against his creator, usually for his own purposes.

In other words, he is the main character in his own series, along with Mega Man.