Following are a number of back-translations as well as a sample translation for translators of Isaiah 14:6:

• Kupsabiny: “He crushed people in anger
  and did not rest,
  and he persecuted those people he ruled
  without showing mercy to them.” (Source: Kupsabiny Back Translation)
• Newari: “Which had always been beating people in anger,
  and, having unbearably suppressed nation after nation, had given [them] suffering and trouble.” (Source: Newari Back Translation)
• Hiligaynon: “that in their anger they have not stopped their cause-to-suffer to the people, and there is no holding-back their persecution to the nations.” (Source: Hiligaynon Back Translation)
• English: “You attacked people many times
  because you were very angry with them,
  and you subdued/conquered other nations
  by causing them to suffer endlessly.” (Source: Translation for Translators)