5. Killing Off Their Villains
This is an issue for many superhero movies. Rather than playing the long game, villains are too often killed off for a new bad guy to take their place in the sequel. Loki's three appearances have countered this somewhat, but those that Earth's Mightiest Heroes face off against remain one of the weakest parts of most of Marvel's movies. It's even become something of a trend now, with critics pointing out forgettable and easily dispatched villains. Think back to the Red Skull, Malekith, Ronan the Accuser, and Iron Monger; all great characters who could have had lengthy story arcs over a series of movies, wasted with a one-off appearance ending in their deaths. This is an infuriating habit, and one which sadly shows no signs of slowing down. Looking ahead to the future, here's hoping the door is left open for Ultron to return somewhere down the line. The fact that fans still desperately want the Abomination to pop back up should show Marvel that viewers want more great recurring baddies, so fingers crossed.