Someone who is relentless is determined to do something and refuses to give up, even if what they are doing is unpleasant or cruel. Relentless in his pursuit of quality, his technical ability was remarkable + relentlessly re·lent·less·ly She always questioned me relentlessly
{s} severe, harsh, unrelenting; inexorable; never-ceasing; that does not relent; unyielding
Something bad that is relentless never stops or never becomes less intense. The pressure now was relentless. + relentlessly re·lent·less·ly The sun is beating down relentlessly
Unmoved by appeals for sympathy or forgiveness; insensible to the distresses of others; destitute of tenderness; unrelenting; unyielding; unpitying; as, a prey to relentless despotism
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"