Has an AFL game ever ended 72-21?
Exactly once. On August 14, 1909, Carlton beat Fitzroy 72-21, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 72-21 in league history.
That makes 72-21 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 73-21 has happened 1 times and 72-22 has happened never.