[Spoon]

There are so many factors that go into decisions like this it makes my head hurt. A lot of good points and Doom seems to be the popular choice. Also, aren't Heroes considered a Villain by Villains?

If Franklin Richards or Hulk were a villain, they'd be the hands down choices for me. Who knows, maybe Franklin Richards is Dr. Doom or somehow created him and his Doombots. Anything is possible in the MU with a retcon or some sliding time scale alternate universe stuff. At one point Doom and Kang were meant to be related instead of Nathaniel Richards.

I'd pick Apocalypse, Doom, Kang & Ultron for different reasons.

Mr. Sinister, Red Skull and Shadow King are characters I'd like to think could have a shot depending on how they are used.

My Marvel knowledge doesn't extend far past the mid 90's. I'm currently reading Avengers Essential Volume 4. This covers issues from '69-'72.