The difference between Largely and Plentifully

When used as adverbs, largely means in a widespread or large manner, whereas plentifully means in a plentiful manner.

check bellow for the other definitions of Largely and Plentifully

Largely as an adverb:

In a widespread or large manner.
Largely as an adverb:

For the most part; mainly or chiefly.

Examples:

"They were largely successful in their efforts."
Largely as an adverb:

On a large scale; amply.
Largely as an adverb (obsolete):

Fully, at great length.