Ma is a concept featured in the final chapters of the God Mazinger manga. Essentially it is a word to represent the evil presence in the souls of sentient lifeforms that when accumulated and nutured can cause crises like a war that can destroy an entire planet. Such an event happened on the Earth back when it was named Eden by the Creator. In this case the God Mazinger acts as a force to eliminate Ma by removing any and all trace of it, even with the destruction of an entire planet.
After the God Mazinger is destroyed after its battle with Demon King Hades, it is reformated but goes on a rampage based on its creator's view that it was used to destroy enemies in front of it. In essence, it came to the conclusion that everything is considered dangerous. However, Yamato convinces the creator that he fought with the Mazinger out of love for Aila Mu. After seeing the love between Yamato and Aila first hand, the creator gives humanity another chance; but if Ma accumulates again, the God Mazinger will reappear and destroy humanity.
The kanji used for Ma (魔) can mean demon, evil spirit, or evil influence.