Evil twin

 The evil twin is an antagonist found in many different fictional genres. The twin is physically nearly identical to the protagonist, but with a radically inverted morality. In films, they may have a symbolic physical difference from the protagonist—such as a goatee beard, eyepatch, scar, or distinctive clothing—which makes it easy for the audience to visually identify the two characters. Sometimes, however, the physical differences between the characters will be minimized, so as to confuse the audience. Both roles are almost always played by either the same actor or the actor's actual twin (if the actor has one).

Though there may be moral disparity between actual biological twins, the term is more often used figuratively: the two look-alikes are not actually twins, but physical duplicates produced by other phenomena (e.g. alternate universes). In other cases, the so-called "evil" twin is a dual opposite to their "good" counterpart, possessing at least some commonality with the value system of the protagonist.