The Terror of Rome Against the Son of Hercules (1964)

In this sword and sandal fantasy, a gladiator named Poseidon must battle a quartet of combatants in ancient Rome. If he wins, the son of Hercules will have his life and anything else he wants. Sure enough, he wins and asks that the life of a Christian girl be spared. But the girl refuses her liberty until all of her fellow believers are also released.