If you’re breaking down which characters Shakespearean characters are the most influential, Prince Hamlet obviously ranks first. He’s the first action hero, after all. However, I’d contend that Iago of Othello (the trusted, but deceitful, ensign who ruined the titular Moor's life by convincing him he'd been cuckolded by his wife and lieutenant) would have to be the silver medalist in this particular line-up. He’s the model of paradoxical, scheming evil who’s inspired many memorable heels--both directly and indirectly--in space operas and urbane thrillers alike.
Attempting to identify and analyze all the villains inspired by Iago throughout the collective cinematic cannon (let alone the “blazing world” of fiction) would be reaching way too far for our purposes here, of course. Thus, we’ll keep the discussion focused on only a few fairly recent, flashier ones…
Wouldn’t you know it: Ian McDirmid has come out and said that Iago was one of his major points of identification for portraying this Lord of the Sith. Lucas is infamous for often giving his actors little instruction other than “faster, more intense.” However, when the cat was finally let out of the bag after Revenge of the Sith and McDirmid was at last free to talk about his "dual role" as Chancellor Palpatine and Darth Sidious, he revealed that he’d been instructed to play the Sith Lord's “public guise” as if he were wearing contact lenses at all times. In effect, it was like "honest Iago" standing up to a politician's intergalactic podium.
Palpatine’s agenda is far more straightforward and ferociously evil than Iago's, to be sure, but for as prominent a role as this arch villain plays in the saga, he's actually defined by the same sort of ambiguities. Was he actually the murderous apprentice he describes in that "Tragedy of Darth Plagueis?” Could he be Anakin’s “father” through the Sith’s unholy manipulation of midi-chlorians? Does he sincerely care for Anakin's success, or is his apprentice only ever a weapon to him? We never have concrete answers to those questions (although I'm sure they're in who-knows-how-many Expanded Universe novels) and we're never quite sure which of his statements are true. He sheds crocodile tears and turns Jedi knights, Sith apprentices and Naboo queens against each other, just as Iago stepped back and let basically all of Venetian neighbors fight among themselves,
Envy fuels Iago’s motivation, and there’s certainly room to interpret his envious obsession with Othello’s professional and romantic life as homosexual in nature. Ripley, at least as depicted in this film, has a similarly complicated obsession with the very identity of Dickie Greenleaf, the wealthy heir whom he's been hired to fetch back home. Again, charming lies are his tools of villainy, not outward brawn, and he gets so deep into his deceptions that he loses his sense of self and, really, a grasp of his own desires. He grows so detached, you don't get the sense that he's truly enjoying what he's gained from his criminal escapades--rather, he's acting out of the joyless compulsion to exercise his "talent."
Call it insubstantial coincidence, but Ejiofor actually played Othello opposite Ewan “Obi-Wan” McGregor’s Iago on stage once. Six degrees of separation connect Shakespeare--or Star Wars--to everything else.
There is something to be noted in how Whedon described this guy as something like "the nicest, politest cold-blooded murderer in the universe" and how “honest Iago” endears himself to so many players despite his awful misdeeds. Still, the Operative isn't much of a deceiver, so a a stronger connection to Iago actually lies in how they both have an unsettling awareness and detachment about their own evil. The Operative freely admits to being a monster who’s committed atrocities in the name of a perfect society he’ll subsequently have no place in, and such a statement gives the impression of there being almost two personalities in him. I imagine if Mal hadn't given him his "wake-up call," he may have developed the same confusion of motivations as Iago does once his lies catch up to him.
Kenneth Branagh memorably played Iago opposite Laurence Fisburne’s in Othello, and it’s clear the role shaped this reinterpretation of the god of mischief, as it differs greatly from the cackling trickster of the comics. Not only does Loki covet Thor’s place as Odin's favored son and use the power of suggestion to get him banished but also, as the film unfolds, we see that his goals are confused even to himself. When he reveals that his whole scheme was actually an effort to actually get Thor on Asgard's throne and groom him for the position along the way, you get the sense that lying has gotten so canny that even he can't tell the difference anymore.
There you go: some proper dinner conversation points to impress your friends with. If you've read Othello, or seen it performed in any capacity, go on and list some other movie villains whom you think owe honest Iago a debt. If you haven't, I do encourage you to experience some version of it. You'll see many of your favorite bad guys with a deeper understanding, I guarantee.