For me this is easy. The grandest fictional monster ever is Dracula. He came long before there was Darth Vader, Lord Voldemort, and Hanibal Lecter.
Dracula is a sympathetically mysterious character. You feel for him, but you’re also terrified by him. Vampires, in general, have that characteristic unlike the Mummy, the Werewolf, or Zombies. I will not count vampires that glitter in the sun.
And this reminds me again of one of the greatest lessons of my writing career. There are NO villains. There are only heroes that have fallen. I don’t always agree with that, but it makes me think about the antagonists in my story. Do they have any iota of humanity left? I think they need to for them to really have staying power. The best villains, the ones that will live beyond us, have that quality.
Who is your favorite monster of all time? Also, here’s a little taste of me thinking I can act, trying to portray Dracula on stage. Enjoy the giggles.