Following are a number of back-translations as well as a sample translation for translators of Isaiah 29:20:

• Kupsabiny: “Then, those people who persecute people shall be no more,
  and those who despise others are no more.
  Every sinner shall be cleared away.” (Source: Kupsabiny Back Translation)
• Newari: “People who have no mercy —
  even their names will be completely destroyed.
  Slandering talk will disappear completely,
  and those who put their eyes to evil work will be destroyed completely.” (Source: Newari Back Translation)
• Hiligaynon: “Because the cruel/ruthless and the people who mock will-disappear. All who are fond of doing sins will-die” (Source: Hiligaynon Back Translation)
• English: “There will be no more people who ridicule others
  and no more arrogant people.
  And those who plan to do evil things will be executed.” (Source: Translation for Translators)