Sacrificed his daughter, Iphigenia.
Agamemnon is angry at Calchas because the seer reveals that the plague ravaging the Greek army is a punishment from Apollo for Agamemnon's dishonor of Chryses, a priest of Apollo. Calchas advises Agamemnon to return Chryseis, the captive woman he took as a prize, to her father to appease the god. Agamemnon feels humiliated and threatened by the loss of his prize and the implication that he must submit to the will of a god and the advice of a seer, leading to his wrath towards Calchas.
Achilles discovers the cause of the plague on the Greek camp through a consultation with the seer Calchas. Calchas reveals that the plague is a punishment from Apollo because Agamemnon has dishonored the priest Chryses by refusing to return his daughter, Chryseis. To appease Apollo and end the plague, Agamemnon must return Chryseis and offer a sacrifice to the god. This revelation sets off a chain of events that heightens the conflict between Achilles and Agamemnon.
The prophet Calchas is reluctant to explain the cause of the plague because he fears revealing the truth may anger powerful figures, particularly Agamemnon, and lead to dire consequences for himself. He understands that the revelation could implicate Agamemnon in wrongdoing, creating a potential conflict. Additionally, Calchas may be concerned about the repercussions of his prophecy on the morale of the Greek forces, as it could lead to further discord among them during a critical time in the war.
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.
Artemis had a very small part in the Trojan War. Unlike the other gods, she had no loyalties to either side before the war. However, since her brother Apollo supported the Trojans, she took Troy's side. This won her the wrath of Hera, who already hated the huntress because Zeus favored Artemis more than any of Hera's children. In the Iliad book 21, Hera boxed Artemis' ears with the girl's own hunting bow. Artemis then fled, with many tears running down her face, to her father Zeus. She left her bow and arrows behind her, leaving her mother Leto to gather them up. Artemis also delayed the warrior Agamemnon and his forces from getting to Troy. Right before Agamemnon was supposed to sail to Troy, he shot one of Artemis' sacred stags in a grove and boasted that he was a better hunter than the goddess Artemis herself. In revenge, Artemis commanded the winds to keep blowing Agamemnon's ships back to shore. Agamemnon then asked an oracle or a seer what to do to appease the god that was preventing his arrival to Troy. The oracle or seer told him that the only way to appease Artemis, the goddess he had angered, was to sacrifice his oldest daughter, Iphigenia, to the goddess. Agamemnon tricked his wife Clytemnestra into sending Iphigenia to him by saying that Iphigenia was going to be married to Achilles, the greatest Greek warrior. When Iphigenia arrived, Agamemnon placed her on the sacrificial alter. Some accounts say that Iphigenia was sacrificed to Artemis, but others say that Artemis replaced her with a white deer at the last moment and took her to an island where the goddess made Iphigenia her priestess. Some stories even say that Iphigenia was transformed into Hecate, the goddess of magic and the dark side of the moon.
Artemis was angry because the Greeks had killed one of her favorite animals, a hare and its young, and wouldnt be appeased untill Agamemnon slayed his daughter. Artemis was appeased but she still had the side of the Trojans, not the Greeks. =) This came from "The Iliad" or the book "Edith Hamilton Mythology"
Agamenon took his girl, Bryseis. Poor guy.
artemis did not because she was a myth.
Aegisthus killed Agamemnon because he sought revenge for Agamemnon's father, Atreus, who had wronged Aegisthus' family in the past. Additionally, Aegisthus was also motivated by his desire to take Agamemnon's throne and power for himself.
Agamemnon, principal chief of the gathered Greeks (as he was king of Mycenae and all of Achaea) took a woman named Chryseis as a slave. Her father, a priest of Apollo, praed for her return, so Apollo sent a plague among the Greeks. The prophet, Calchas, after being sworn protection by Achilles, told Agamemnon that Chryseis needed to be returned to end the plague. Agamemnon agreed, but also declared that Achilles' slave, Briseis be brought to him as a replacement. Achilles, raging over the dishonor (and because he loves Briseis), prays to his mother, Thetis, for Zeus to help the Trojans gain the upper hand.
Nestor tells Achilles and Agamemnon that it is sad to see the Greeks divided and that they should pay attention to his wise words. He tells Achilles that he should not think he can fight against a king and that Agamemnon is greater than he is because he rules over more people. He then tells Agamemnon that even though he is powerful, he should not take Briseis because the Greeks gave her to Achilles as his prize of honor.
Menelaus and Agamemnon were called the Atridae because their father was named Atreus.