Final answer:
Colonel John Chivington sought revenge on Native Americans at Sand Creek for the death of his family in the Sand Creek Massacre.
Step-by-step explanation:
The person seeking revenge on Native Americans at Sand Creek for the death of his family was Colonel John Chivington. In what became known as the Sand Creek Massacre, Chivington led a militia raid on a camp of Cheyenne natives who had negotiated a peaceful settlement. Despite the camp flying both the American flag and the white flag of surrender, Chivington's troops brutally murdered close to one hundred people, mostly women and children.