7. Ultimatum
Ultimatum (which is a story from the Ultimate Marvel universe) occurred when both the Scarlet Witch and Quicksilver (Magneto's daughter and son) were killed. Scarlet Witch was (supposedly) killed by Ultron and Quicksilver was killed by Hawkeye whilst protecting Magneto from one of his arrows. Both the Scarlet Witch and Quicksilver are due to appear in the Avengers sequel, Age of Ultron, and in an ideal world this could easily lead in to the Ultimatum storyline. If the Scarlet Witch was to die, this could prompt Ian McKellen's Magneto to appear - angered at the situation she was put in fighting alongside the Avengers - and, as he battles the Avengers, Hawkeye's arrow could be intercepted by his son. This could send him in to the rage that prompted the Ultimatum storyline. Vowing revenge for his childrens' deaths ("for what they have done, they must pay the ultimate price"), Magneto triggers a doomsday device that sets off a series of disasters around the world, prompting a number of heroes (including the Avengers, X-Men, Spider-Man and the Fantastic Four - the latter of whom are expected to join the X-Men movie continuity sooner rather than later) to help in rescue efforts. The likes of Thor, Iron Man, Wolverine, Spider-Man, Cyclops and Mister Fantastic all find themselves battling Magneto and his Brotherhood forces (which include the likes of Sabrethooth, Blob and Multiple Man), which leads to a final battle that actually reveals Doctor Doom as the mastermind behind the series of events (including Scarlet Witch's death) that led to Magneto going all genocidal - though he didn't expect that to be the outcome, he just wanted to overthrow humanity himself. It would make for an epic crossover movie involving some of the best characters from all three respective franchises and would come with a fantastic tagline (as spoken by Magneto): "When God didn't like what he created, he washed it all away in forty days and forty nights. I will do it in three."