If you are referring to Sparta, the Greek city state, it never defeated the Romans. If you are referring to Spartacus, he defeated the consular armies of Lucius Gellius Publicola and Gnaeus Cornelius Lentulus Clodianus.

Lucius Brutus established the Republican form of government.

There were two annually elected consuls after the deposition of the kings. The first two consuls were Lucius Junius Brutus and Lucius Tarquinius Collatinus. Collatinus was the husband of Lucretia, the woman whose rape triggered the revolt and the overthrow of the monarchy. He had to resign because of complaints about his being part of the royal family. His place was taken by Publius Valerius Publicola.

An ancient Roman military leader, Lucius Cornelius Sulla.

Roman Consul Lucius Aemilius Paullus.