relentless

adjective2

1. •
   Unrelenting or unyielding in severity.

   • She sniffed, too, comprehendingly, and fixed her son with a relentless eye. — 1930
2. •
   Steady and persistent; unremitting.

   • In Clintonworld, the reaction to Grassley’s relentless assault on Huma is one of resignation. — 2016