Magento (X-Men movies) vs. Green Goblin (Spider-Man) vs. Doc Octopus (Spider-Man 2) vs. Vemon (Spider-Man 3) vs. Whiplash (Iron Man 2) vs. Abomination (Incredible Hulk) vs. Red Skull (Captain America) vs. Dr. Doom (Fantastic Four) vs. Loki (Avengers)
@Jade1977: I think it will come down to Magneto and Abomination.
Loki is a God but he didn't really do much in the movies besides command other people and he was man-handled by Hulk in the movie and the Abomination was pretty comparable to the Hulk.
If Magneto can keep his distance, he could impale everybody or smash everybody with metal. Abomination could withstand a lot of the abuse.
Goblin/Ock/Venom/Whiplash go down quickly. Skull hangs on for a little bit but overwhelmed by the power of Loki/Abomination/Magneto.