Palpatine: "It wasn't wrong, Anakin. It may be not the Jedi way, but it was right. Perfectly natural— he took your hand; you wanted revenge. And your revenge was justice."
Skywalker: "Revenge is never just. It can't be—"
Palpatine: "Don't be childish, Anakin. Revenge is the foundation of justice. Justice began with revenge, and revenge is still the only justice some beings can ever hope for. After all, this is hardly your first time, is it?"