Above all. In the first place; chiefly.

I had also studied Virgil's design, his disposition of it, his manners, his judicious management of the figures, the sober retrenchments of his sense, which always leaves somewhat to gratify our imagination, on which it may enlarge at pleasure; but above all, the elegance of his expression, and the harmony of his numbers. Dryden's Dedication to the Æneid.