relentless
词根词缀：
词根
lent= loose 松
relent v. 放松；变宽厚
re 一再 + lent 松 → 一再松开 → 放松
relentless adj. 无情的
relent 放松；变宽厚 + less 无…的 → 不宽厚 → 无情的
后缀
-less 表形容词，“无…的，不…的”
数据来源：新东方英语词汇速记大全
相关例句：
Experienced relentless evolution of time, life has become tough do?
经历了时间无情的嬗变，生命曾经变得坚韧吗？
His relentless aggression bludgeons you into seeing his point.
他咄咄逼人地强迫你了解他的看法。
Here is a truth about the parents of a child with a disability: We are relentless.
这是一个关于身为“问题儿童”父母的真理：我们是不留情面的。
Relentless and indefatigable in pursuit or as if in pursuit.
不懈的、不知疲倦的在追求或者好像是在追求。
We will be relentless in defense of our citizens and our friends and allies.
我们会一直保护我们的居民、我们的朋友和盟友。
Relentless in his pursuit of quality, his technical ability was remarkable
对质量孜孜不倦的追求使他的技能出类拔萃。