Assassins Who Cleanse Sins Away

This world is surrounded by crime, greed, and many other sins. Though in time people gave up hope for peace then a group of assassins changed that and now they cleanse the city they live in. They even take clients around the world. If you're truly tormented by anyone and want vengeance then you must contact those assassins but vengeance comes with a price and it doesn't mean your life. Those assassins are called The Sweepers and no one knows who they truly are.