Dai-Mazinger (大魔神我, Great Mazin-Me) was a plan for an OVA remake of Mazinger Z in 1986. The project was proposed by Masami Ōbari and other notable indepedent animators not associated with Toei Animation, with permission from Dynamic Productions. However, the project was cancelled as Toei held the rights to the Mazinger animation.
Dai-Mazinger originally was held in tight secrecy until information leaked out at a conference and magazines. There was an image that showed the mecha design but Ōbari revealed on his twitter account the image was fake. The characters from the original series were meant to appear along with a more realistic looking Mazinger, including the use of a Rocket Punch that does not return.
Decades later, the name would be used in a new project, that eventually came into be Mazinger Edition Z: The Impact!, various designs and ideas that were devloped through the years would be used later originated in the Dai Mazinger idea, like Big Bang Punch.