or Pe7xQd8=R#?
Longest individual notation?

or maybe (if you could capture during castling) then maybe a double disambiguated capture long castle unaccepted draw check/mate? (while also capturing a double disambiguated queen)
so a1RO-O-Oxc1Q=#?
Qg2xd5# and things in that format is probably longest. I can't think of anything longer because the only extension to notations are +, # and x and x and (# or +) can come together plus one piece then a square than x than the square it moves to then + or #.

I thought f7xRg8=Q# would be the longest, since that is 9 characters without any ? or ! but I could be completely wrong
It might be e5xd6ep#. The move e5 indicates that the pawn started at e5. The notation xd6 shows that the pawn captured an opponent’s piece and landed on d6. The "ep" signifies that the pawn took the opponent's piece en passant. Also, the hashtag indicates Checkmate. And the Notation has 8 Characters.
ep is not mandatory and dosent show up on chess.com if you try exd6# (there is no 5 because no two pawns on the same file can move to the same square) and # is possible. Here is my best demonstration.
Bc6xd5# (the famous double disambiguated bishop mate), O-O-O+ or O-O-O# (long castles mate), or even Qh4xe1# (2x disambiguated queen mate) etc. are the only ones I am aware of... There could also be exd8=Q+... But I cant say I have seen more the seven letters in one move!!
I thought f7xRg8=Q# would be the longest, since that is 9 characters without any ? or ! but I could be completely wrong
The issue is that the notation would actually be fxg8=Q#... Because we will write f7 only if two pawns can make the same move, ., on f7 and on h7. Also, there should be no "R", because when captures happen, we never write the captured piece... Hope it helps!
Many pawn moves can ocur in games, each of which resets the 50-move count. Probably the game can extend to like 2000 moves? (if White is the player to wipe out the entire army of Black, then the maximum number of pawn pushes is 6 x 8 = 48, while the maximum number of captures is 15, so the absolute maximum number of moves in the game without a 50 move rule being claimed is (48 + 15 + 1) x 50 = 3200, while the maximum number of moves without meeting the 75 move automatic draw is (48 + 15 + 1) x 75 = 4800,texas roadhouse calories but it is hard to achieve the first 50 moves without captures, pawn pushes and breaching the threefold repetition rule).
Yes i see this
so maybe e7xQd8=R#?