Proverbs 21:29 New English Translation

²⁹A wicked person^[a] has put on a bold face,^[b]
but as for the upright,^[c] he establishes^[d] his ways.

Proverbs 21:29 tn Heb “a wicked man.”
Proverbs 21:29 tn Heb “he has strengthened his face.” The Hifil of עָזַז (ʿazaz) “to cause to be strong” is used idiomatically with “face” meaning to show boldness. Similarly the seductress in Prov 7:13 had put on a bold/impudent face. This person makes a show of confidence, either to be persuasive or to divert their own attention from the substance of a matter. Their confidence is not backed up by reality.
Proverbs 21:29 tn The “upright” is an independent nominative absolute; the pronoun becomes the formal (emphatic) subject of the verb.
Proverbs 21:29 tc The Kethib is the imperfect of כּוּן (kun), “he establishes.” This reading has the support of the Syriac, Latin, and Tg., and is followed by ASV and NASB. The Qere is the imperfect tense of בִּין (bin), “he understands; he discerns.” It has the support of the LXX and is followed by NIV, NCV, NRSV, NLT. The difficulty is that both make good sense in the passage and both have support. The contrast is between the wicked who [merely] puts up a bold front and the upright who either [actually] discerns his ways (Qere) or makes his ways solid (Kethib). And whichever reading is chosen, the meaning of the other is implied. It would not make sense for the verse to talk about someone who understands but does not act accordingly; on the other hand, to make his/her way solid, the upright person must understand it.

New English Translation (NET)