Learn Swedish: Späckhuggaren är faktiskt en gigantisk delfin. - The killer whale is actually a gigantic dolphin.

It is a compound noun made of späck (blubber or animal fat) and huggare (someone or something that strikes, chops, or bites). So, a killer whale is literally a "blubber biter"! Breaking down long Swedish compound words into their roots is a great trick for expanding your B2 vocabulary.

Is faktiskt related to the English word "factual"?

They share the same root, but faktiskt is a bit of a false friend. It almost always means "actually" or "in fact", just like in this sentence. If you want to say that a document or statement is "factual" (based on facts), you would instead use words like faktaenlig or faktamässig.

How would I use the preposition på to specify that it is a "gigantic dolphin of 8 meters"?

You would simply add the phrase directly after the noun it describes: Späckhuggaren är faktiskt en gigantisk delfin på 8 meter. In Swedish, the preposition på is the standard way to attach specific measurements, sizes, or ages to a noun, replacing the English use of "of".

What happens to the word order if I emphasize faktiskt by moving it to the very start of the sentence?

Because Swedish strictly follows the V2 (verb-second) rule, the verb är must stay in the second position. If you put the adverb first, the subject (späckhuggaren) has to swap places with the verb, making it: Faktiskt är späckhuggaren en gigantisk delfin.