Why did Clytemnestra kill Agamemnon?
To get revenge. He sacrificed their daughter Iphigenia at Aulis to appease Artemis so that the Greek fleet could sail to Troy. Also, he brought home Cassandra as a concubine. (Aeschylus’s Agamemnon ln 1438-1443, 1524-1526) Earlier he did killer her previous husband and child in order to marry her, but the more predominant theme seems to be Iphigenia’s sacrifice.