Icelandic vs. Swedish

Hi!

Please can someone help me with a bit of complicated linguistic conceptualisation? This is about 2 adjectives with opposite meanings which have double forms, in this case bad (in Swedish) and good (in Icelandic).

1. In Swedish:

dålig, värre, värst (the usual bad/worse/worst)

dålig, sämre, sämst (the comparative forms refer to less of a good quality)

2. In Icelandic:

góður, betri, bestur (the usual good/better/best)

góður, skárri, skástur

So, it would seem to me that Swedish HAN ÄR SÄMRE is the exact opposite of Icelandic HANN ER SKÁRRI.

This strikes me as deeply interesting. I know of nothing similar outside the Scandinavian languages. Any comments? What happens in Danish/Norwegian/Faroese?

Is there a specific Icelandic equivalent of dålig, sämre, sämst? And is there a specific Swedish equivalent of góður, skárri, skástur?

Cheers,

Simon