Relentless is a related term of unsparing.
As adjectives the difference between relentless and unsparing
is that relentless is unrelenting or unyielding in severity while unsparing is without sparing.
relentless
English
Adjective
(
en adjective)
Unrelenting or unyielding in severity
Unremitting, steady and persistent
Derived terms
* relentlessness