Has an AFL game ever ended 58-21?
Exactly once. On May 11, 1901, Melbourne beat St Kilda 58-21, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 58-21 in league history.
That makes 58-21 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 59-21 has happened 1 times and 58-22 has happened never.