As Spanish I think the most important kings were Isabel the Catholic, Carlos I and Felipe II, many consider substitute of Isabel to Carlos I, probably because in his reign "Spain achieved its maximum extent", but really it was not.
Although Carlos was king of Spain and emperor of the holy Roman empire does not mean that the holy Roman empire was part of Spain.
Furthermore he was a foreigner and folksy king who did not speak Spanish and did not understand the traditions of the kingdoms of Spain, which will led to the wars of the commoners in Castile. It is true that then learned Spanish and was gradually adapting but it was especially the Holy Roman Emperor before the king of Spain, and his interest was to wage war by the Holy Roman Empire and not for the welfare of Spain.
Instead, Felipe II has been very, very badly treated by the "Spanish black legend". But he really was one of the best kings that Spain has had, their concern was to ensure the Spanish hegemony in Europe, its expansion by America and stop the Ottomans in the Mediterranean, improved administration (he was one of the kings who have worked more by Spain, if not the most), succeeded in unifying the Iberian Peninsula (Portugal and its colonies were annexed, kingdom that was part of Spain for about 60 years). He was not a cruel king, it is more after the defeat of the invincible navy, the black legend attributed him an attitude of indifference and the following sentence << I did not send my ships to fight the elements >> (phrase was invented 40 years later of the death of Felipe II by Baltasar Porreño), but it is completely false, when the navy was defeated was a blow for him and had a caring attitude with disaster survivors, unlike Elizabeth I of England who abandoned to their fate to 9000 English sailors who became ill after the war.
In conclusion, he was not a perfect king, much less. Yet Felipe II was a king who was concerned about Spain, loved his people, and worked tirelessly to improve the kingdom, a rare type of king in Spanish history.
So if developers of Civilization VI have read this for a casual, and decide to put Spain in the base game or DLC / expansion and want to switch to Isabel the Catholic for a change of leaders, please consider to Felipe II, and in his bibliography put their real life and not unjust lies of the black legend.
Thank you for reading and for your patience by my level of English.

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