Cassandra

In Greek mythology, Cassandra was a daughter of king Priam of Troy, who captured the eye of Apollo and so was given the ability to see the future. However, when she did not return his love, he placed a curse on her so that noone would ever believe her predictions. Thus Cassandra foresees the destruction of Troy, the death of Agamemnon, and her own demise, but is unable to do anything about them. She figures prominently in a few tragedies for obvious reasons.