8. Anakin vs. Younglings - Star Wars: Episode III - Revenge of the Sith
Given how absolutely badass Darth Vader looked in the esteemed "original trilogy" of Star Wars, George Lucas certainly had his work cut out for him when deciding how to cement Anakin's transformation into said badass in his hugely-anticipated closer, Revenge of the Sith. As it turns out, Lucas doesn't put much effort into making him a fiersome foe, but ends up making him sympathetic, and his most vicious moment throughout is when he slaughters a room of defenceless "Younglings", baby Jedis who are clearly having a class of some kind, before Anakin shows up and cuts them all down. Now, this occurs off-screen, but the mere inference is enough; Star Wars, even in its most menacing moments, is pretty light-hearted and broad, but this is a savagely violent moment by sheer implication alone, such that it'll be burned onto a generation of children's minds with the searing heat of a lightsaber itself.