Strong H5358 נָקַם nâqam · to avenge

Genesis

1. Genesis 4:15
   And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him.
2. Genesis 4:24
   If Cain shall be avenged sevenfold, truly Lamech seventy and sevenfold.