Developed ones.

A more serious answer: each country has impoverished neighborhoods. The difference between developed countries and developing ones is the magnitude of the impoverished neighborhoods.

So far I haven't seen any really big slums in Germany, for example.

Then you obviously havent been to Halle/Silberhöhe. But as you said, the difference is the magnitude. The scale of informal economies is certainly higher in Brazil, Honduras or Colombia. While here, even in problematic spots of certain cities, you will have the occasional criminal, the economic situation of a whole city is not dependent on it.

Apart from a few trailer encampments of sinti/roma there really aren't. Those usually get demolished after a few month.

how is comparing a small affluent country to a large and econ diverse one even remotely fair?

i would not be aware of one in switzerland

a handful of small, affluent European nations. That's it