Conversation so far:
What were the reactions to Juan Carlos I of Spain's abdication?
The Spanish press gave it a broadly positive reception. In Spain and in major cities, it was met by republican celebration and protests, calling for the end of the monarchy.
Did Juan Carlos I of Spain have any other roles?
On paper, Juan Carlos retained fairly extensive reserve powers. He was the guardian of the constitution, and was responsible for ensuring that it was obeyed.
What happened to Juan Carlos I of Spain after the reactions from the Spanish press and major cities?
Juan Carlos's image was further tarnished in 2018 when recordings of conversations of an alleged mistress, Corinna zu Sayn-Wittgenstein, with a former police chief were leaked to the press.

Question: How long was he King?
Self-contained rewrite: How long was Juan Carlos I of Spain king?