deadly vs pernicious

deadly and pernicious both are adjectives.

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

As adjectives, deadly and pernicious are synonyms defined as:

Other synonyms of deadly include baneful, pestilent.

deadly (adjective)	pernicious (adjective)
exceedingly harmful	working or spreading in a hidden and usually injurious way
extremely poisonous or injurious; producing venom	exceedingly harmful
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

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