Agreed re Krakow.Yup, seconded. Malaga Centro is way too small, and most of the C-1 line is appalling. Whether it's the long single track sections, the constantly broken lifts (hello, Fuengirola) or the simple awful stations (hello, Torremolinos), the line has absolutely nothing going for it. For all the money spent on the airport section, they really could have just committed to dualling the entire line. That's before we even talk about the endless will-they-won't-they situation with the extension to Marbella and beyond.
Really? I quite like Petržalka - it's airy, not busy and gets the job done without fuss. It's not dingy or falling apart, and the only 'bad' thing is that they haven't bothered to tear down the old passport/customs control area so that the concourse can be extended. But IMO, it's a good example of a 90's station that was built for a purpose - the trains to Vienna and potentially local trains to Hungary.
From what I understand, the problem with the old passport/customs area is that the Slovak police still use that area on occasion, so they don't want to give it up.
As for my most hated, some of the new Polish stations are awful. Kraków Główny is a disgrace (essentially platforms stuck on a shopping mall) when you consider that the historic station is still there, Poznań Głowny is too small and not finished and so on... I'm also not a fan of some of the modernised ex-DDR stations, particularly Fredrichstrasse and Ostbahnhof.