Sorry to bother you, but this is really starting to eat my brain.
I saw this Mecha-anime/movie at some point of the 80's.
it's quite similar to Tranzor z with the flying fist and all.
I dont remember much but i recal "him" living inside of a mountain (human made headquarters), fighting monsters and even kicking one's head of with a curved blade that came out from the side of his leg.
Thank you for reading.