In the dialogue with the people of the small, weak island of Melos, the Athenians explained why the island must submit to the wishes of the city of Athens: "the strong do what they can and the weak suffer what they must." (P. 352, Landmark edition) Yow. That is (as the headline suggested) perhaps the nastiest line I ever have read.
The Melians asked to be allowed to remain neutral in the war. Tough luck, said Athens, which then invaded and "put to death all the grown men whom they took, and sold the women and children for slaves," and then re-settled the island with their own colonists.
Such wholesale violence seemed to be about par for the course in the ancient Greek world. Samos is not that big an island, but when one party in a civil war on the island prevailed, it executed 200 of most powerful men from the other party and banished another 400. (P. 493, Landmark edition) Sounds to me like they extirpated the opposition.