Has an MLB game ever ended 20-4?
It has. 20-4 has been a MLB final 24 times in 235,971 games. The first was Philadelphia Quakers beat Detroit Wolverines on June 6, 1883; the latest was Los Angeles Dodgers beat Miami Marlins on September 19, 2024.
That makes 20-4 the 169th most common final score out of 330 that have ever occurred in MLB. One point away, 21-4 has happened 10 times and 20-5 has happened 22 times. At one point the score disappeared for 36 years, between 1957 and 1993.