To the very highest degree — better (or worse) than anything else of its kind. It goes in front of an adjective and pushes it to the top: superlatively good, superlatively talented, superlatively dull. "The food was superlatively good." It is stronger than very and stronger than extremely, because it does not just say "a lot" — it says "nothing beats this". That is the flavour of the Latin root: superlative means the top form of an adjective (big, bigger, biggest — biggest is the superlative). The word is formal and literary, the kind of thing a critic writes in a review of a concert, a restaurant, or a book. In everyday talk nobody says it; we say incredibly, amazingly, or just the best. Because it is so grand, writers also use it with a dry, ironic tone for bad things — "a superlatively boring afternoon" — where the joke is that even the boredom was world-class.

極其、無與倫比地（正式、書面用語，程度最高）