Mazinger Z vs The Great Dark General (1974)

Original title: マジンガーZ対暗黒大将軍

Deep beneath the earth, seven robots lay dormant: a human, a mammal, a bird, a fish, an insect, a reptile, a ghost... and the Great General of Darkness.

Kouji and his friends have defeated Dr. Hell and are now enjoying a break, but suddenly a strange prophet appears and warns everyone of an oncoming danger, mechanical beasts never seen before start appearing all around the world wrecking havoc. Its up to Kouji and his Mazinger Z to stand up to this threat but it seems he is vastly outnumber and outmatched.