ku-adjective (archaic)
Archaic ku-adjective meaning 'best' or 'superb'. In modern Japanese, it is almost exclusively used in the adverbial form こよなく, meaning 'exceptionally' or 'above all'.
See also: こよなく
こよなき幸せを感じる。
I feel the greatest happiness. (archaic/literary)
現代では「こよなく愛する」のように副詞形で使われることが
In modern times, it is often used in the adverbial form, as in こよなく愛する (love dearly).