So indeed the Nuremberg network seems pretty complicated if you seek weird combinations (in your case, apparently, be in 2 different towns the same day for a cheap price).
But I think it depends on criteria, and some cities have pretty complex ones. The number of transit systems, the number and complexity of pricing schemes, the complexity of getting information on whole system, ...
I have a couple examples of pretty complex systems. San Francisco has 1 city network, a train (BART) that links different parts of the Bay, a bus network for North Bay, a train for commuters in South Bay, ferries, ... Every system has different pricing strategies. The BART has no month or day pass, and you pay depending on distance. You also pay depending on distance on the South Bay train, but there are passes. The City system has a pass or $2 single ticket. If you use the three systems, you can still have a single electronic card to load all different passes/cash on it.
A second example is in Nice, France area (and probably a lot of other cities in France). There are 3 city systems for transit, a train linking them and a coach network linking the cities too. You may need to have a train pass, a city pass and still buy tickets when you go to the next town. There is still one pass giving access to 3 networks for affordable price.
I have never been there, but I heard Tokyo subway is pretty complex too. There are lots of companies operating a connecting network and you should pay depending on your departure/arrival combination. I don't know exactly how it works, but it's still kinda complex.