Israel is another candidate, given that Israel has beef with Spain for Spanish government not supporting/approving the genocide in Gaza.
I don't believe that without evidence. Europe tacitly supports Israel even while some parts of it claim not to, and Spain is internationally irrelevant.
This makes no sense.
Israel responds to words with words. They respond to force with force. And they are busy enough dealing with the trouble that Iran keeps stirring up, they're not going to do anything to Spain. (Not to say that it would be out of the question for them to go after terrorists who were in Spain, but it would be very focused. Look at what happened after Munich--multiple European countries were incredibly inept about extraditing the attackers so Israel responded with assassination teams. Not strikes on anything they didn't believe had hurt them.)
(And there never was a genocide, but this isn't the thread for it.)