adj. 25B6; adjective
their relentless pursuit of quality : PERSISTENT, continuing, constant, continual, continuous, non-stop, never-ending, unabating, interminable, incessant, unceasing, endless, unending, unremitting, unrelenting, unrelieved; unfaltering, unflagging, untiring, unwavering, dogged, single-minded, tireless, indefatigable; formal pertinacious.
a relentless taskmaster : HARSH, grim, cruel, severe, strict, remorseless, merciless, pitiless, ruthless, unmerciful, heartless, hard-hearted, unforgiving; inflexible, unbending, uncompromising, obdurate, unyielding.