前功尽弃

前功盡棄
qiángōngjìnqì
  1. to waste all one's previous efforts (idiom)
  2. all that has been achieved goes down the drain

CEDICT

all previous achievements go down the drain; all the previous effort is wasted

Wiktionary

将以往辛苦建立的功劳，全部废弃。《史记．卷四．周本纪》：「今又将兵出塞，过两周，倍韩，攻梁，一举不得，前功尽弃。」《红楼梦．第一三回》：「如何肯又回家染了红尘，将前功尽弃呢？」也作「前功皆弃」、「前功尽灭」、「前功尽废」。

重編國語辭典

Entry Composition

1 前功 qiángōng
  1. (literary) previous achievements; previous deeds
  2. previous achievements; previous deeds
2 尽 jìn
  1. to use up
  2. to exhaust
  3. to end
  4. to finish
  5. to the utmost
  6. exhausted
  7. finished
  8. to the limit (of sth)
  9. all
  10. entirely
3 弃 qì
  1. to abandon
  2. to relinquish
  3. to discard
  4. to throw away