Inspired by the success of The Dark Knight’s Joker, io9 has some thoughts on keeping your villains villainy – what makes them great, how they go wrong, and how not to ruin their effectiveness. Darth Vader is used as an example in the last – and I can’t say I disagree.
While Anakin’s redemption in Return of the Jedi (and the subsequent “I hate sand”ing of the prequels) may have made him a more fully rounded character, as a villain that’s a quite bit of defanging – fitting for one of the few truly gray characters in the very black and white, good vs. evil world of Star Wars, but maybe not the best recipe for a purely terrifying cinema baddie.
In any case – that’s what we have Palpatine for. We don’t need a troubled childhood, the truth about Plagueis, or his inner monologue: He’s just there. He’s manipulative, he’s evil, he takes over the galaxy. That’s all you need. Thankfully (so far) Lucasfilm realizes this.
Now honestly, when it comes to novels, I tend to lean more towards villains with shades of gray, and be more critical of those who come across as a more simple evil. (In theory, this would include the New Jedi Order’s Yuuzhan Vong – if they hadn’t just been so damn boring. Hell, maybe that’s why they were so boring – they should have stayed in Galaxy Quest.) It’s the virtues of the medium – in a book or series you have more time and space to develop the villains and get into their head space. But taking a decent cinema villain to paper takes a fine touch – something the EU hasn’t always managed.