Has an AFL game ever ended 75-18?
Exactly once. On July 3, 1897, Fitzroy beat St Kilda 75-18, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 75-18 in league history.
That makes 75-18 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 76-18 has happened never and 75-19 has happened never.