unrelenting

unrelenting
    adj 1: not to be placated or appeased or moved by entreaty;
           "grim determination"; "grim necessity"; "Russia's final
           hour, it seemed, approached with inexorable certainty";
           "relentless persecution"; "the stern demands of
           parenthood" [syn: {grim}, {inexorable}, {relentless},
           {stern}, {unappeasable}, {unforgiving}, {unrelenting}]
    2: harsh; "the brutal summer sun"; "a brutal winter" [syn:
       {brutal}, {unrelenting}]
    3: never-ceasing; "the relentless beat of the drums" [syn:
       {persistent}, {relentless}, {unrelenting}]
    

Unrelenting \Un`re*lent"ing\, a.
   Not relenting; unyielding; rigid; hard; stern; cruel. --
   {Un`re*lent"ing*ly}, adv. -- {Un`re*lent"ing*ness}, n.
   [1913 Webster]
    

137 Moby Thesaurus words for "unrelenting":
      adamant, adamantine, assiduous, cast-iron, constant, continuing,
      de longue haleine, diligent, dogged, dour, endless, enduring,
      extended, faithful, filled out, firm, flinty, fundamentalist, grim,
      hard, hard-core, hidebound, immovable, immutable, implacable,
      impliable, inalterable, indefatigable, indomitable, industrious,
      inelastic, inexorable, inflexible, insistent, intransigent,
      invincible, iron, ironbound, ironclad, ironhanded, irreconcilable,
      lasting, lengthy, long, long-drawn-out, long-spun, long-winded,
      longiloquent, loyal, merciless, mortal, muscle-bound, never-tiring,
      obdurate, obstinate, orthodox, padded, patient, patient as Job,
      permanent, perseverant, persevering, persistent, persisting,
      pertinacious, plodding, plugging, preoccupied, procrustean, prolix,
      protracted, purist, puristic, puritan, puritanic, rapt, relentless,
      resolute, rigid, rigorist, rigoristic, rigorous, rock-ribbed,
      rockbound, ruthless, sedulous, single-minded, sleepless, slogging,
      spun-out, stable, steadfast, steady, steely, stern, stiff,
      straightlaced, straitlaced, stubborn, talkative, tenacious,
      tireless, unabating, unaffected, unalterable, unappeasable,
      unbending, unchangeable, uncompromising, unconquerable, undaunted,
      undiscouraged, undrooping, unfailing, unfaltering, unflagging,
      unflinching, ungiving, unintermitting, uninterrupted, unmoved,
      unnodding, unrelaxing, unremitting, unsleeping, unswerving,
      untiring, unwavering, unwearied, unwearying, unwinking, unyielding,
      utterly attentive, verbose, weariless, windy, wordy