Relentless vs Pernicious - What's the difference?

As adjectives the difference between relentless and pernicious

is that relentless is unrelenting or unyielding in severity while pernicious is causing much harm in a subtle way.

(en adjective)

Unrelenting or unyielding in severity

Unremitting, steady and persistent

* relentlessness

(en adjective)

Causing much harm in a subtle way.

* 1911 , ,

Puritanism no longer employs the thumbscrew and lash; but it still has a most pernicious hold on the minds and feelings of the American people.

Causing death or injury; deadly.

* (l)

* perniciousness * perniciously