Has an AFL game ever ended 45-21?
Exactly once. On June 25, 1898, Melbourne beat St Kilda 45-21, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 45-21 in league history.
That makes 45-21 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 46-21 has happened never and 45-22 has happened 1 times.