Final answer:
The Punic Wars were the series of conflicts that established Rome as the dominant power in the Mediterranean Sea.
Step-by-step explanation:
The conflict that left Rome as the most powerful force on the Mediterranean Sea was the Punic Wars. The First Punic War, lasting from 264 to 241 BCE, marked the beginning of Rome's struggle against the Carthaginians for Mediterranean supremacy. Initially confined to Sicily, Rome's victory in the war led to its annexation of the island, laying the groundwork for future expansion. Successive conflicts, namely the Second and Third Punic Wars, saw Rome cementing its control over the Carthaginian territories, leading to Rome's unmatched power across the region by 140 BCE.