Has a La Liga game ever ended 8-0?
It has. 8-0 has been a La Liga final 25 times in 27,754 games. The first was Real Sociedad beat Racing Santander on March 19, 1933; the latest was FC Barcelona beat Deportivo La Coruna on April 20, 2016.
That makes 8-0 the 27th most common final score out of 51 that have ever occurred in La Liga. One point away, 9-0 has happened 12 times and 8-1 has happened 21 times. At one point the score disappeared for 29 years, between 1967 and 1996.