lifelessly vs deadly

lifelessly is not an adjective while deadly is an adjective.

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

As adverbs, lifelessly and deadly are synonyms defined as:

lifelessly (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

lifelessly (adverb)	deadly (adverb)
as if dead	(used as intensives) excessively
without animation or vitality	as if dead
in a lifeless manner