Has an AFL game ever ended 77-9?
Exactly once. On July 16, 1898, Essendon beat Carlton 77-9, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 77-9 in league history.
That makes 77-9 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 78-9 has happened never and 77-10 has happened never.