不遗余力

不遺餘力
bùyíyúlì
to spare no pains or effort (idiom); to do one's utmost

CEDICT

to do all one can; to do one's utmost; to spare no effort; to go all-out

Wiktionary

毫不保留，竭尽全力。

重編國語辭典

毫不保留，竭尽全力

維基詞典

Entry Composition

1 不遗 bùyí
  1. (literary) to not leave; to not abandon; to not leave out
  2. to not leave; to not abandon; to not leave out
2 余力 yúlì energy left over (to do sth else)