Absolutely not Ottos 2nd. Castile is 2nd, if not first.
What stands in Castile's way? Guaranteed Alliance with France if you don't fuck it up, meaning the only major threat to you can't stop you. You get the only PU in the game that gives FREE integration of massive amounts of land (can vary if Aragon invades north italy, if they take Rome, Ancona, if they integrate Naples first, etc). That PU alone propels you into Italy, giving you an easy time boosting your income.
Not only that, but Paradox adding some more minor states in the Mahgreb, including releasable Fez, means UNLIKE previous patch, Castile can gobble up North Africa (by vassalizing and feeding) without the Berber traditions +100% coring cost. Making that area incredibly easy to expand into, especially since it's virtually impossible for Castile to lose to the Arabs there, unless you are brain dead.
Next, Castile isn't just Castile. Castile is Portugal+Castile+Aragon, realistically. You can lock Portugal out of colonizing before they even colonize. No one else has this ability. This means before Portugal gets a single colony (even if they get 1 or 2, it's not a huge issue) they will be your vassal. Since Portgual is the 2nd best colonizer in the game, that means Castile is essentially 2 nations who are able to colonizing from the very start of colonization. South America and the Caribbean are 100% yours. Mexico is basically yours, unless you don't prioritize colonies properly and France/England sneak a few in there. In my experience with the patch, EVEN WITH THE DOUBLED NEW WORLD PROVINCES, you can STILL coast lock the rest of the Europeans, minus Canada. Canada, and maybe 3-4 Caribbean islands are the only places you will not colonize first, but it's irrelevant since it's incredibly easy to take them and just give them to your colonial nations. In my last Spain game I was able to almost get 100% of the US. The only place missing was a small, small amount of Vermont/Maine area in the north, which was easily feed-able to my nation. The only colonizing area you can't secure are the Islands in South East Asia, simply because there are so many. However you can secure Australia 100%, Philippines, and most of the important larger islands you can colonize.
All of this along with marriage+alliance with France for 100% of the game. On top of that, although unlikely, you can luck into inhereting burgundy. My previous game I got a PU because they took my Dynasty, oddly enough. This was followed SHORTLY after by Austria falling into a PU with me, and much much later I enforced a PU with France and Venice, making anything France managed to colonize mine anyway.
No one seems to touch West Africa, so by the time you are ready to move into there you can have the increased Admin Efficiency and you can sweep through the entire reagon within 30-40 years.
This is all in addition to taking over any nations in South East Asia, India, Arabia, etc through out the game.
Pics for reference. Note that in this France, Portugal, Brittany, Flanders, the Pope, and Venice are all under my rule. France and Venice in a PU, the rest are vassals.
I would argue Spain is most capable of World conquest. With the right ideas your economy will skyrocket, and your military will be unstoppable. Their national idea's give 5 discipline, and 15% morale. You can instantly convert anything with religious ideas, no matter how many provinces you take so your nation is incredibly stable throughout the entire game. You can just spam the Papacy for 1% mercantilism all the time because of Spains +2 papal influence. While the rest of Europe is pissing on each other, Spain just fucks off to the rest of the world and uses their alliance with France as a buffer. No threats to them what-so-ever.
This is all without a single coalition forming. Spain is the only major nation in the game, bar maybe england, who can form an empire this size without getting a coalition against them. France is obscenely better at the start, but 1 province into the HRE and they have no where to expand. As well as relying on heavy luck to inherit burgundy, and a TERRIBLE Navy that prevents them from really going against england very easily. Spain+Portugal in 1500 can easily hold off a player France. Plus, their end node is garbage, and since England, Spain, and Portugal are infinitely better colonizers/naval powers, goodluck getting trade back from the new world. France is heavily overrated simply because of their armies. Admittedly Ai france rarely, if ever, falls, and a war against them early is borderline impossible to win, but if you are a nation that is really going up against france, just take quantity and quality and call them a day. They can't expand fast enough to outscale you on manpower and force limits because of their Aggressive Expansion problems in the HRE.
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