Dancouga: Super Beast Machine God

Story

Deep in outer space, the emperor Muge plots his next conquest - an out-of-the-way planet known as Earth. Mustering all the forces of his own personal Empire of Death, the Emperor is by far the most formidable foe humans have ever faced. And now he's even more fearsome thanks to the defection of Shapiro Keats, a power-hungry Earthling reborn as an Empire informer. Army after army crumbles in the face of an onslaught of the Empire's seemingly indestructible robots.

Synopsis via AniList (English).