Following are a number of back-translations as well as a sample translation for translators of Proverbs 12:20:

• Kupsabiny: “People who make conspiracy plots love to cover the eyes of people (make people not see),
  but happy is a person who brings peace.” (Source: Kupsabiny Back Translation)
• Newari: “The hearts of the wicked
  are always full of evil thoughts,
  but good thoughts will bring rejoicing.” (Source: Newari Back Translation)
• Hiligaynon: “Cheating is in the heart of a man who plans bad, but joy is in the heart of a man who plans good.” (Source: Hiligaynon Back Translation)
• Kankanaey: “Tricks/Deception is what exists in the mind of one-who-plans evil, but happiness is what exists in/with one-who-causes-there-to-be harmony.” (Source: Kankanaey Back Translation)
• English: “Those who plan to do what is evil are always wanting to deceive others,
  but things will go well for those who plan to do good things.” (Source: Translation for Translators)