Has an AFL game ever ended 89-20?
Exactly once. On June 17, 1989, Geelong beat Melbourne 89-20, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 89-20 in league history.
That makes 89-20 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 90-20 has happened never and 89-21 has happened never.