Denmark
Denmark is, by default, the enemy state of all Swedes. This is not a casual rivalry. This is historically validated dislike. These two have fought an absurd number of wars in the Medieval period, to the point where it feels less like history and more like a long-running series with too many seasons. If there was a leaderboard for "most unnecessary fights," this region would dominate it.
These days, no one is swinging swords anymore. The hatred has been optimised. It now exists as friendly-hate. The kind that shows up in jokes, passive-aggressive comments, and very serious football and ice hockey matches. It is less "I will conquer your land" and more "I will absolutely not let you win this game." Progress.
Living close to Copenhagen creates a strange dynamic. On one hand, it is extremely convenient. The airport is excellent. Connectivity is smooth.
But then...
It is so fucking expensive. Not mildly expensive. Not "okay this is manageable" expensive. Properly, aggressively expensive. The kind where you start doing real-time currency conversion in your head and immediately regret every life decision that led to buying that coffee.
Second, the language. Danish is what happens when Swedish is processed through chaos and someone adds a hot potato into the speaker's mouth for good measure. Words exist, but they do not want to be heard. Consonants disappear. Sounds blur. Entire sentences feel like they are being whispered underwater. It is technically a language, but it behaves like it is actively trying to avoid being understood. I myself, tried learning the language on Duolingo after having completed all levels in Swedish (flex), but I gave up after 10 levels.
That said, it's not all hate. Places like Legoland Billund and the Roskilde Viking Ship Museum suggest a country that knows how to package history and entertainment properly. There is real cultural identity underneath the jokes, even if it is filtered through centuries of rivalry.
So the current state of affairs: mild hostility, frequent interaction, reluctant appreciation.
Denmark is close enough to visit often (which I'll be doing), different enough to complain about every time (which also I will be doing), and familiar enough that the complaints are part of the experience.