True, the adjectives are opposites of one another. Feo = ugly and bonito = pretty/ beautiful.
there are 4 groups of adverbs in german
Adverbs of Place
Adverbs of Time
Adverbs of Manner and Degree
Adverbs Indicating Cause
i found this on https://www.thoughtco.com/learning-german-adverbs-1444449 if you wanna look your self hope this helped