Mazinger Z vs. The Great General of Darknes (1992)

Dr Hell and his lieutenants were finally defeated after a long battle. The Mazinger team take a beach day, but then a storm brews in from the intense heat. Boss and his gang see a vision of a prophet who warns them of the Great General of Darkness who will attack the earth from the land, sea, and air to cause the end of the world as people knew it. The only hope for survival was the Mazinger Z. 

Mazinger Z vs Great General of Darkness is a film retelling of the beginning of the Great Mazinger manga. Before the finale of the Mazinger Z anime, the film was made to introduce the Great Mazinger and the Mycenae Empire before the Great Mazinger anime premiered.