Following are a number of back-translations as well as a sample translation for translators of Isaiah 9:21:

• Kupsabiny: “Manasseh shall fight against Ephraim,
  and Ephraim fight against Manasseh
  and then both shall join forces against Judah.
  But the anger of God is not subsiding,
  since he still wants to punish those people.” (Source: Kupsabiny Back Translation)
• Newari: “Manasseh will eat Ephraim and Ephraim [will eat] Manasseh,
  then they will both go against Judah.
  But his anger will still not subside,
  and his hand will still be lifted.” (Source: Newari Back Translation)
• Hiligaynon: “Manases and Efraim will-fight, and the two of them will-attack Juda. But the anger of the LORD still will- not -be-stopped. He is still ready to punish them.” (Source: Hiligaynon Back Translation)