She had softened perhaps from her yesterday's relentlessness.
How could he stand there so like a machine in his relentlessness?
She felt oppressed by the hardness, the 136 relentlessness, of his words, his manner.
Mr. Reade traces their history with all the relentlessness of the genealogist.
And this one, though not so powerful, frightened me the more in his relentlessness.