諍友

诤友
zhèngyǒu
a friend capable of direct admonition

CEDICT

  1. (literary) friend who will give unreserved criticism
  2. friend who will give unreserved criticism

Wiktionary

能直言規勸的朋友

維基詞典

Entry Composition

1 諍 zhèng
  1. to admonish
  2. to warn sb of their errors
  3. to criticize frankly
  4. Taiwan pr. zhēng
2 友 yǒu friend