mightily vs mighty

mightily is not an adjective while mighty is an adjective.

Word	Noun	Adjective	Verb	Adverb
mightily	No	No	No	Yes
mighty	No	Yes	No	Yes

As adverbs, mightily and mighty are synonyms defined as:

mightily and mighty: (Southern regional intensive) very; to a great degree

Other synonyms of mightily include powerful, right.

mightily (adjective)	mighty (adjective)
	having or showing great strength or force or intensity

mightily (adverb)	mighty (adverb)
(Southern regional intensive) very; to a great degree	(Southern regional intensive) very; to a great degree
powerfully or vigorously