Like:
- PLC: They make a great ally and only expand into eastern Europe. If you're TO, Brandenburg, Muscovy, Hungary etc. it's easy enough to strike them down early.
Maybe if you strike super early you can prevent Poland and Lithuania teaming up, but it becomes awkward after that. (Breaking the PU is one thing, but you also have to break the 'historical friends' modifier.) If you don't, it's a huge amount of development to chew through even if you have the means to crush them on the battlefield.
- Sweden: They are mostly irrelevant to European Alliance systems since they rarely make an impact. But they rival you the very instant you do something on the Baltic and annoy the hell out of you with their strait, super soldiers and winter if you actually have to fight them, without offering nice territory to take.
Except the Copper Mountain. Always take the Copper Mountain for yourself as soon as you can.
- Ming: Their troops are not particularly hard to beat if you do not play something little/rotw obsessed but it's always such a draged out war.
While it stays intact, Ming annoys me not so much for what it can do, but for the bonanza of Broken China that I'm missing out on. Broken China is basically a second India for any European who wants to carve out an easy trade empire in Asia (or just a regular land empire in Asia), except that if the Ming vase has only just hit the concrete, it's much quicker and easier to conquer than India (given that India tends to consolidate into a few blobs if it's left alone for a while).