Has an NFL game ever ended 28-0?
It has. 28-0 has been a NFL final 42 times in 18,234 games. The first was Dayton Triangles beat Detroit Heralds on November 25, 1920; the latest was San Francisco 49ers beat Los Angeles Rams on September 12, 2016.
That makes 28-0 the 137th most common final score out of 1,095 that have ever occurred in NFL. One point away, 29-0 has happened 5 times and 28-1 has happened never.