不遗余力用英语可以说作 "give it one's all"。这个表达来源于拼音译音，"不遗余力" 的拼音是 "bù yí yú lì"，而 "give it one's all" 的读音与之相似。

例句：

I will give it my all to make sure this project is a success. 我会不遗余力地做好这个项目。

She gave it her all in the race, but unfortunately came in second. 她在比赛中不遗余力地拼搏，但不幸地获得了第二名。

We need to give it our all if we want to win this game. 如果想赢得这场比赛，我们就必须不遗余力。