Learn Finnish: He löysivät avaruudesta mullistavimman innovaation. - They found the most revolutionary innovation in space.

It starts with the verb mullistaa (to revolutionize). We first form the present active participle mullistava (revolutionary). Its superlative form ("most revolutionary") is mullistavin. Because it describes the total object of the sentence, it must be in the accusative case. The stem of mullistavin is mullistavimma-, and adding the -n object marker gives us mullistavimman.

Why does the sentence use avaruudesta (from space) when the English translation says "in space"?

The verb löytää (to find) always dictates a "from" case in Finnish, usually the elative (-sta/-stä) or ablative (-lta/-ltä). While in English you find something "in" a location, Finnish logic says you discover it "out of" that location.

Why do mullistavimman and innovaation end in -n instead of being in the partitive case?

They form the total object of the sentence. The act of finding is a completed action resulting in a fully achieved goal. For singular nouns and their modifiers, the total object takes the accusative case, which is marked by an -n ending, making it look identical to the genitive case.