This is the 8426th most frequent Russian word.
наибольшее
"Наибольшее" means "the greatest" or "the largest."
Here, 'наибольшее' is used as a superlative adjective meaning 'greatest', modifying the noun 'значение' (significance).
Наибольшее значение этого достижения трудно переоценить.
The greatest significance of this achievement is hard to overestimate.
Here, 'наибольшее' is used as a superlative adjective meaning 'highest', modifying the noun 'количество' (quantity).
Он получил наибольшее количество голосов на выборах.
He received the highest number of votes in the election.
Here, 'наибольшее' is used to emphasize the intensity and importance of the attention to be focused.