remorseless

From remorse + -less.

remorseless (comparative more remorseless, superlative most remorseless)

1. Without remorse, mercy or pity.

   Synonyms: merciless, pitiless, ruthless; see also Thesaurus:cruel

   Antonym: remorseful

2. Unyielding or relentless.
   • 1968, Christopher Hodder-Williams, “Hands”, in Fistful of Digits, London: Coronet Books, published 1972, →ISBN, page 125:

     She was, in fact, constitutionally impervious to statistics and preferred to study the be-headphoned group of fifteen or so lethargic wanderers who were taking even less notice of the remorseless squawkings than she was.