If I had to support a Spanish team, it would be Betis just because their fans are fucking mental.
And they hate Sevilla so much they let themselves get beaten just to see Sevilla get relegated.
https://www.espn.com/soccer/spanish-laliga/story/4602414/sevillareal-betis-is-laligas-best-rivalryand-in-a-city-that-lives-for-the-sport