Good, or at least memorable quotes by bad people. Some may be fictional...
“Faith moves mountains, but only knowledge moves them to the right place.” - Joseph Goebbels. Yes, I've looked at the context, and of course everything he said was in furtherance of atrocities.
“Voice or no voice, the people can always be brought to the bidding of the leaders. That is easy. All you have to do is tell them they are being attacked and denounce the pacifists for lack of patriotism and exposing the country to danger. It works the same way in any country.” – Hermann Goering
“Do not compare yourself to others. If you do so, you are insulting yourself.” - Hitler. Only memorable because it's widely attributed to him. Whoever first said he said it must have been feeling extra mischievous.
“One death is a tragedy; one million is a statistic.” - Joseph Stalin. Misattributed, as it turns out. It just sounds like something he would have said.
“You know, a long time ago being crazy meant something. Nowadays everybody’s crazy.” - Charles Manson
"To read too many books is harmful." - Mao Zedong. He didn't mean reading was bad, but that bookishness combined with dogmatism was.
"Hidden talent counts for nothing." - Nero. More likely to have been Phaedrus, a contemporary of Nero. But he's not known to have fiddled.
Ezra: "I'm not afraid of you!"
Vader: "Then you will die braver than most."
"If you think this has a happy ending you haven't been paying attention." - Ramsay Bolton