Cassandra

In Greek mythology, Cassandra was a Trojan prophetess, the sister of Helen and the daughter of king Priam and queen Hecuba. She was gifted her powers by Apollo, as a revenge for having turned him down – she would be able to see the future, but was cursed never to be believed.
Cassandra predicted the destruction of the city of Troy, because of Paris – who abducted Helen, thus starting the war with the Greeks, narrated in the Iliad – but no one believed her.
When the Trojan Horse (which was probably a ship – turned into a horse by a mistaken translation of the Greek word hippos) was already inside the city walls, and the city was doomed, the Trojans were celebrating and getting drunk, sure that they had won the war. The Greeks came out of the Horse at night, slaughtered the Trojans, and burned down the city.
After the fall of Troy, Cassandra was abducted by Agamemnon. She prophesized his ruin too, and once again she wasn’t believed. She died together with Agamemnon in a conspiracy lead by Agamemnon’s wife.