devilishly vs deadly

devilishly is not an adjective while deadly is an adjective.

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

As adverbs, devilishly and deadly are synonyms defined as:

Other synonyms of devilishly include deucedly, insanely, madly.

devilishly (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

devilishly (adverb)	deadly (adverb)
in a playfully devilish manner	(used as intensives) excessively
(used as intensives) excessively	as if dead
as a devil; in an evil manner