Summary
King Felipe VI of Spain faced a hostile crowd in Valencia, where unprecedented floods have devastated communities, leaving over 200 dead and many missing. Footage shows protesters shouting “murderer” and “shame” at the king, with some throwing objects and mud as he walked through the affected area of Paiporta.
There is also a King of Denmark, England, Norway, Sweden, Belgium and a King of the Netherlands. But most monarchies are constitutional so they hold no political power.
The British monarch does hold political power, but usually does not do anything with it.
https://en.wikipedia.org/wiki/Monarchy_of_the_United_Kingdom#Constitutional_role
Hence “most”.