I don't want to step on CrimsonRash's toes here, but as I helped co-write and edit, as well as writing a few chapters myself, CHAPTER 3: LOVE IN AN ELEVATOR and CHAPTER 4: WORKED OUT (with heavy edits by CrimsonRash), and CHAPTER 9 (I think...the numbering gets pretty complicated): POSITIVE REINFORCEMENT (aka the boring chapters, because I'm not great at writing fights, so instead I wrote backstory and psychological torment and humiliation) I will try and sort a few things out.
The BLACK CAT vs MARY JANE started as a great one-off story by CrimsonRash some years ago that I really loved...so much so, in fact, that I wrote a continuation based on his original, which then prompted him to contact me and we started to collaborate on expanding the series, which he did the lion's share of the work. In all we collaborated on some 10 chapters, nine of which were completed, and most of which were released. I can't actually recall if POSITIVE REINFORCEMENT has actually even been released because somewhere along the line we went back and revised the old chapters to create a "Perfect Version" of the series that would tie everything together more uniformly (at the times the originals were written they were not part of a series and the continuity was pretty loose...so we decided to go back and tighten things up and tried to role with changes in the actual Spider-man continuity, such as incorporating Mephisto, though we both agreed that BRAND NEW DAY was fucking stupid so we ignored the idiotic unmarrying). I believe we got up to revising BLACK CAT vs INVISIBLE WOMAN when a combination of writers block and personal obligations put the brakes on things.
As it stands now; there are 9 completed chapters, and the 10th and final chapters is about 90% finished, but remains incomplete.
It remains my personal favorite catfight story of all time, and even though I wrote quite a bit of it myself, I still re-read it pretty regularly, and I'm glad that others have found enjoyment in it. It really spoke to my love of female dominance, real physical and emotional stakes, rivalry, and superheroics...as well as huge tits.^_~ I have only ever read one other BC vs MJ catfight story that's come close by UnknownFan, but it does not have nearly the depth that we tried to put into this series.
Most of the chapters have been spread around the internet, but I don't know that the "Perfect Versions" have been published in their entirety online...four of those chapters are on RedhotRash's DeviantArt page, the rest are on our hard drives.