Following are a number of back-translations as well as a sample translation for translators of Jeremiah 14:20:

• Kupsabiny: “Oh, God, we have rebelled against you
  and we accept that also the forefathers have sinned against you,
  truly, the sin we have done is not small!” (Source: Kupsabiny Back Translation)
• Hiligaynon: “O LORD, we (excl.) acknowledge our (excl.) wickedness and the sin of our (excl.) ancestors. We (excl.) really have-sinned against you (sing.).” (Source: Hiligaynon Back Translation)
• English: “Yahweh, we admit/know that we are wicked people,
  and that our ancestors also did many wicked things.
  We have all sinned against you.” (Source: Translation for Translators)