This is the 278th most frequent German word.
komplett
Complete; entirely.
The word 'komplett' is used here as an adverb to describe the extent of the renovation.
Das Haus ist komplett renoviert.
The house is completely renovated.
In this sentence, 'komplett' functions as an adverb emphasizing the completeness of the action of reading.
Er hat das Buch komplett gelesen.
He has read the book entirely.
Here, 'komplett' modifies 'falsch', emphasizing the totality of the error in the statement.