4) Athletic Bilbao 10-0 Celta Vigo (1942)
Athletic Bilbao are one of the legendary clubs in Spanish football history. They are one of the founders of the La Liga along with Real Madrid and Barcelona. Bilbao have never been relegated from the top flight of Spanish football since its inception.
The San Mames based club have won 8 La Liga titles and an amazing 24 Copa Del Rey titles. Bilbao are a regular feature in the conversation of biggest wins in La Liga.
The 1941-1942 season saw the Basque club beating Celta Vigo 10-0. In the same season, Sevilla beat Oviedo by the same margin in what were the fourth biggest win margins in the La Liga. In the 1950-1951 season, Athletic Bilbao beat Lleida by the same margin. It was the second time in the season that Lleida had conceded ten goals in a match.