Has an AFL game ever ended 51-25?
Exactly once. On June 20, 1908, Essendon beat Geelong 51-25, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 51-25 in league history.
That makes 51-25 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 52-25 has happened never and 51-26 has happened never.