Following are a number of back-translations as well as a sample translation for translators of Proverbs 21:15:

• Kupsabiny: “If/When justice/truth is done, it makes the righteous people happy,
  but (it) threatens/terrifies sinners.” (Source: Kupsabiny Back Translation)
• Newari: “When justice takes place the righteous rejoice.
  and the wicked tremble.” (Source: Newari Back Translation)
• Hiligaynon: “If justice will-prevail, the righteous rejoice, but the evil-ones are nervous/worried.” (Source: Hiligaynon Back Translation)
• Kankanaey: “Those who are doing what is right are made-happy when justice is put-forth (i.e. accomplished), but sinners are afraid.” (Source: Kankanaey Back Translation)
• English: “Good/Righteous people are happy when they see others do what is just/fair,
  but those who do what is evil are terrified when they think about what may happen to them.” (Source: Translation for Translators)