for the most part vs largely

for the most part and largely both are adverbs.

Word	Noun	Adjective	Verb	Adverb
for the most part	No	No	No	Yes
largely	No	No	No	Yes

As adverbs, for the most part and largely are synonyms defined as:

Other synonyms of for the most part include mostly.

for the most part (adverb)	largely (adverb)
in large part; mainly or chiefly	in large part; mainly or chiefly
	on a large scale