Nederen covers more emotional ground than lame does - from my understanding of lame, which is really not.. a word close to me. It was heavily in use among teenage boys when I was a teenager. Nederen can be disparaging, but for some reason really calls to my mind almost-crying teenagers breaking up with each other. So! Can convey hurt if your emotional vocabulary is supremely stunted! Can lame? (I mean, can sucky? But I think it can? In an equally stunted way)
It's hard to tell the "sweariness" of a word in Danish as everybody (almost) use swearwords all the time (cabinet ministers on the telly, children's television, whatever).
This is not a critique against the Danish language, just a warning that swearwords might be seen quite differently in Danish than in many other languages. If you speak English to a Dane you might experience that he swears a lot, this is the same thing working in reverse: he translates what is normal speach for him.
it's always hard to keep up with the latest slang and usage, especially the wide geographical scope in English, so think you need to be liberal in accepting translations here... suck, lousy, lame, etc... all seem fine to me. but "sucky" with the Y strikes me as a very juvenile/dated expression fwiw.
I wish people who downrated your comment would tell you why. My comment had two personal observations, first that I've never heard this usage in real life, and second my speculation that the usage might be linked to the age of the speaker. If someone disagrees with that, they must either think that it's reproachable that I haven't heard this word use or that there is something offensive about suggesting that a certain age group would be likely to use it. Now, which is it?