Largely means "to a great extent," "generally," "in great part": "That opinion is largely incorrect." "My reaction will depend largely on the kind of answer I get." Chiefly, a stronger word than largely, means "principally," "mainly," "essentially": "My interest is chiefly in the salary." Related words include notably, signally, especially, markedly, and exceptionally.
Dictionary of problem words and expressions. Harry Shaw. 1975.