Bugging me for years. I saw an anime in the early 80's (I assume it was from around then, since I watched it on a VHS tape) that featured a war between a group of pilots, maybe 3 or 4, that could join into 1 giant robot. This robot had a red head with red spikes kind of like the Statue of Liberty. The bad guys had giant robots that could join together too to form 1 giant super robot, and there were maybe 6 of them.
I think it was feature length but possibly several episodes of a series put together. Also it seemed to me to not be childish. It wasn't adult but PG-ish. I recall it being sort of dark and sinister and violent. Please help me. Oh, and it wasn't Voltron or anything obvious like that.