pernicious vs deadly

pernicious and deadly both are adjectives.

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

As adjectives, pernicious and deadly are synonyms defined as:

Other synonyms of pernicious include baneful, pestilent.

pernicious (adjective)	deadly (adjective)
working or spreading in a hidden and usually injurious way	exceedingly harmful
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

pernicious (adverb)	deadly (adverb)
	(used as intensives) excessively
	as if dead