苦心

kǔxīn
  1. painstaking effort
  2. to take a lot of trouble
  3. laborious at pains

CEDICT

Entry Composition

1 苦 kǔ
  1. bitter
  2. hardship
  3. pain
  4. to suffer
  5. to bring suffering to
  6. painstakingly
2 心 xīn
  1. heart
  2. mind
  3. intention
  4. center
  5. core

classifiers: 顆, 個