Myrtilus

Pelops wanted to marry Hippodamia, daughter of King Oenamaus of Pisa. Oenamaus had pursued a dozen suitors of Hippodamia and killed them all. Pelops (or alternatively, Hippodamia herself) convinced Myrtilus, Oenomaus' charioteer to remove the linchpins attacking the wheels to the chariot. Pelops had promised him of the kingdom of Pisa. Oenomaus died. Pelops then killed Myrtilus because he didn't want to share the credit for winning the chariot race, or because Myrtilus had attemped to rape Hippodamia. As Myrtilus died, he cursed Pelops. This was the source of the curse that haunted future generation of Pelops' children, including Atreus, Thyestes, Agamemnon, Aegisthus, Menelaus and Orestes.