This is the 14694th most frequent German word.
naivsten
Superlative form of "naiv" meaning "most naive."
Here, 'naivsten' is used as the superlative form of 'naiv', describing the wish with the highest degree of naivety.
Das war der naivsten Wunsch, den ich je gehört habe.
That was the most naive wish I have ever heard.
Here, 'naivsten' is used attributively before a noun, enhancing 'Annahme' (assumption) to describe its quality of being naive in the highest form.
In einer naivsten Annahme gingen wir davon aus, dass alles einfach sein würde.
In a most naive assumption, we assumed everything would be simple.
Here, 'naivsten' functions to qualify 'Träumen' (dreams), emphasizing their extreme naivety in a hypothetical context.