Not AFL, but I was happily listening to the radio coverage in Tassie of East v North Launceston in the mid 80's. East in front in Q3...then North kicks 10 goals in 7 minutes. That's not an approximation, that was the clock! North by 25 goals...Geelong were involved in a couple of defeats with a scoring surge of similar magnitude in 1986 and in Rd 1 1990. Against Essendon (Jacko's last game) in Rd 2, 1986, Geelong eked ahead of the Bombers 7.4.46 to 6.9.45 during the earlier part of the 3rd quarter, before getting pummeled 21.22.148 to 7.9.51, a turnaround of almost 100 points.
That Rd 1 1990 game, Grand Final rematch with Hawthorn and Geelong, well at VFL park Geelong again nosed ahead in the 3rd quarter by a point before a Hawk explosion where they added 19 goals to virtually zero and turn that narrow deficit into a 115 point whipping.
But in a Grand Final i am sure there's been no reversal of form to that extent, although the Bombers turned a19 pt 3/4 time deficit into a 24 pt win with their famous last quarter against the Hawks in 1984.