The fight in the Big Doll House (1971) was a classic. First fight to go all-in in the mud. Excellent build-up, followed by great action. It's part of my personal collection, which I put together much later when VHS was developed.
I remember watching it in my rear view mirror at the Drive-In. Couldn't take my date to see a women's prison movie, so we went to watch "Clay Pigeon" starring Telly Savalas, which was playing at the same drive in but on a different screen. That movie sucked, but it was bearable considering what I was really watching. We had to be creative back in those days.