madly vs deadly

madly is not an adjective while deadly is an adjective.

Word	Noun	Adjective	Verb	Adverb
madly	No	No	No	Yes
deadly	No	Yes	No	Yes

As adverbs, madly and deadly are synonyms defined as:

Other synonyms of madly include deucedly, devilishly, insanely.

madly (adjective)	deadly (adjective)
	exceedingly harmful
	extremely poisonous or injurious; producing venom
	involving loss of divine grace or spiritual death
	(of a disease) having a rapid course and violent effect
	causing or capable of causing death
	of an instrument of certain death

madly (adverb)	deadly (adverb)
(used as intensives) excessively	(used as intensives) excessively
in an insane manner	as if dead
in an ungovernable manner