Why isn't it
Eine schreckliche nette Familie
? I suspect it has to do with the adjective/adverb dualism, but even then I can't make sense of it.
Why isn't it
Eine schreckliche nette Familie
? I suspect it has to do with the adjective/adverb dualism, but even then I can't make sense of it.
The schrecklich in this sentence is describing the nette. So yes, you were right, the adjective/adverb dualism is the cause.
The schrecklich here indicates that they're awfully nice, or maybe even shockingly nice. It would be a lot more clear if we had more context.
Eine schreckliche, nette Familie
This sentence, note the comma, would mean that the family is both schrecklich and nett.