Fiat Lux

A bunch of political extremists are brawling in the 1930s in Europe. Commies, anarchists, and fascies. An alien ship comes by and scoops them up. They wake up in a starship traveling the Galaxy, and learn their captor is an interstellar explorer that has been disgraced on her homeworld. She listens to them screaming about what their definitions of evil are, and then responds to them by explaining that the race of Man can barely yet tap the fires of the Atom, but her society could rip entire planets asunder without a second thought. She smiles, takes out a vibroblade, and then walks up to the biggest character, a Russian anarchist that had the misfortune to survive until the purges, and kills him without even seeming to make an effort. The rest of the humans attempt to fight her, but she simply slays all except one last survivor, a Communist of the Luxembourgist variety. She walks up to him, and then informs him that as many as the Soviets have killed, that her society can easily kill far more. Her starship disembarks suddenly over a world that is a smoldering ruin, and he asks what happened here. She calmly informs him that prior to her disgrace, she was part of a military detachment that reduced this world, once a powerful starfaring society, to Oldowan-level pebble-chipping technology. The man turns to her in shock, and he suddenly finds himself dropped from the starship, falling...falling...

The moral of this story: just because we think we're the most bad-ass, cruel, vicious monsters in the Galaxy does not make that so.