unrelenting
adj. 无情的；不屈不挠的；不松懈的
例句
The heat was unrelenting.
炎热没有减弱的迹象。
《牛津词典》
She established her authority with unrelenting thoroughness.
她以彻底的一丝不苟树立了自己的权威。
《柯林斯英汉双解大词典》
He was unrelenting in his search for the truth about his father.
他不顾一切地搜集有关他父亲的事实真相。
