critical friend; friend who gives frank advice
A friend who is not afraid to point out your faults or argue with you for your own improvement. The term is somewhat formal and not an everyday word; it carries a classical Chinese flavor.
He is a critical friend to me, someone who gives his honest opinion without reserve.
Having a true critical friend is essential for personal growth.
悪友 is a bad friend or a friend who leads you astray, the opposite of a 争友 who helps you improve.
Standard kanji form; 争 suggests 'contend' or 'dispute', reflecting the idea of a friend who will argue for your own good.
Variant using 諍 (quarrel, dispute); less common but still encountered.
From Chinese 爭友 (zhēngyǒu), literally 'contending friend'. The Japanese reading そうゆう is the on'yomi of the characters. The concept is rooted in Confucian ideals of friendship where a true friend is one who dares to remonstrate.