Every movie involves conflict. The majority of movies have that conflict transpire between opposing sides, personified in the protagonist and the antagonist. Generally this is oversimplified as the hero and the villain, but that's not always true. Sometimes the conflict is simply between characters that have conflicting interests (ex. Indiana Jones and Belloq in Raiders of the Lost Ark).
More often than not, however, the antagonist is old fashioned evil. Upon the introduction of the character, an effective filmmaker will very quickly venture to establish that the villain is evil through their actions.
For example, one of the first things Grand Moff Tarkin does in Star Wars is promise to spare Alderaan if Leia reveals the location of the rebel base. After she's blurted out a (false) name, Tarkin orders the Death Star to blow up Alderaan anyway! There's no indication that Tarkin was aware of Leia's lie; he's just a cruel son of a bitch.
Contrast that with General Grievous in Revenge of the Sith, who never commits an onscreen, blatant act of evil the entire movie. He's described as being a killer of Jedi, and shows off light sabers he's stolen off the bodies of his victims, but never actually kills anyone directly the entire movie.
So what are the best and worst examples of film shorthand for establishing a character's EEEEEEEEEEEEvil ways?