Learn Finnish: Tämä kilpailija laskeutuu hypystä tyylikkäimmin. - This competitor lands from the jump most stylishly.

It comes from the adjective tyylikäs (stylish). To form the superlative adverb (meaning the 'most' version), you take the plural stem of the word, which is tyylikkäi-, and attach the superlative adverb ending -mmin.

Why is hypystä (from the jump) in the elative case (-stä)?

The verb laskeutua (to land or descend) expresses a movement starting from somewhere. Because the competitor is coming 'out of' the action of the jump, Finnish treats it as an origin point and uses the elative case (-stä).

Why does hypystä only have one p when the dictionary word for jump is hyppy?

This is a classic example of consonant gradation. The ending -stä closes the final syllable of the word. When a syllable is closed by a grammatical ending, a strong consonant combination like pp weakens to a single p.

What is the base verb for laskeutuu and how is it built?

The infinitive is laskeutua (to land, descend). It is built from the verb laskea (to lower, put down) by adding the reflexive ending -utua. This ending changes the action from doing something to an object to doing it to yourself, so lowering yourself becomes landing.