2. Thanos
Thanos is on here for a few reasons, but one more than other he was teased at the end of the first damn movie! While the idea of 'keeping Thanos for the finale' is probably the central motivator for him not appearing in Avengers 2, it doesn't make a whole lot of sense to have him as the man behind the scenes of Loki's plot in Avengers, have the Infinity Gauntlet appear in Thor and have the primary focus of two of the Phase One films be an object often associated with him that being the Cosmic Cube if he isn't going to actually show up until at least 5 years after the audience is introduced to him. I mean, that kind of gives way too much credit to the memory and attention spans of the general audience. Also, Guardians of the Galaxy which will be the last bit of Marvel Cinematic exposure audiences will be getting before Age of Ultron seems to be pretty Thanos-heavy in terms of plot. While Thanos isn't slated to appear in it, another movie that seems to be teasing the threat of The Mad Titan would have been a great primer for him to finally appear in his conquest of Earth in Avengers 2. Or perhaps a conquest of Asgard for The Tesseract and the Infinity Gauntlet that are apparently hiding in Odin's vault? Even the comic books seemed to indicate Thanos' involvement in Avengers 2. It doesn't take a keen observer to realize that since the first X-Men movie Marvel has made an effort to make the comic books be as similar as super-humanly possible to the film universe. With two major mini-series springing up this year focusing on Thanos as a central character Thanos Rising and the current crossover Infinity after years of being relatively un-used, it seemed Marvel was priming its readers for a cinematic appearance for the character. But then again, Marvel Entertainment does seem to like their curve balls - *cough* The Mandarin so maybe the plan was to get us looking one way to give us a real surprise. Regardless whether his absence is a mistake of logic or an act of misdirection, Thanos would have made the most sense as the villain for Avengers 2. "But if that's the case, how come he isn't number one?" you may be asking. Well, that's because in my opinion the big baddie of Avengers 2 didn't necessarily need to be a villain...