NET
21 God made the one who did not know sin to be sin for us, so that in him we would become the righteousness of God.
Darby
21 Him who knew not sin he has made sin for us, that *we* might become God's righteousness in him.
KJV
21 For he hath made him [to be] sin for us, who knew no sin; that we might be made the righteousness of God in him.