This is the 244th most frequent Finnish word.
kovin
"Very" or "too" (depending on context).
In this sentence, 'kovin' modifies the adjective 'pimeistä', adding an emphasis that implies a softening of the statement.
En pidä kovin pimeistä elokuvista.
I don't really like very dark movies.
Here, 'kovin' is used as an adverb modifying the verb 'harjoittelee', indicating the intensity or effort.
Hän harjoittelee kovin soittaakseen konsertissa.
He practices hard to play in the concert.
In this context, 'kovin' again modifies the adjective 'suuri', indicating a degree of the described property.