Has an AFL game ever ended 97-20?
Exactly once. On June 19, 1909, Sydney beat St Kilda 97-20, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 97-20 in league history.
That makes 97-20 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 98-20 has happened never and 97-21 has happened never.