Vastly
Part of speech: adverb
Definition: Greatly, in a vast manner.
Example sentence: Great nations are simply the operating fronts of behind-the-scenes, vastly ambitious individuals who had become so effectively powerful because of their ability to remain invisible while operating behind the national scenery.
Immensely
Part of speech: adverb
Definition: Hugely; extremely; vastly.
Example sentence: My opinion, my conviction, gains immensely in strength and sureness the minute a second mind as adopted it.