4. Emperor Palpatine
If Grievous is fearful, The Emperor is downright terrifying. Hiding behind the mask of Chancellor Palpatine, Darth Sidious developed the insidious clone army and ultimately the Galactic Empire. Then, when all seemed done, he emerged again to reign terror with the Final Order. None of that screams holiday season to me.
Palpatine is easily the most treacherous figure in the galaxy. There is also something about his dark robes, though they do receive a nice pop of red in The Rise of Skywalker, that seem more fit for Halloween. Now you might think Chancellor Palpatine, the warm and comforting figure of the Republic would seem like the perfect guest. But his ability to deceive your guests and lure them over to the dark side may cause you to cut ties with a few other friends.
While there are many characters on this list, Palpatine stands alone in his impact, singlehandedly orchestrating the galaxy for decades. Think about what he could do at your holiday party.