7. Resurrecting Agent Coulson
Agents of S.H.I.E.L.D. has transformed into a great TV series, something which is helped a great deal by the inclusion of Clark Gregg's Agent Coulson. After a disappointing start which saw it lose a lot of viewers, the show really found its footing with some Captain America: The Winter Soldier tie-in episodes and has continued to improved massively. Unfortunately, it's the strong inclusion of Agent Coulson that is also one of Marvel's biggest mistakes. To be fair to them, Agents of S.H.I.E.L.D. has done an awesome job of explaining his resurrection and tying it into a wider mythology, but the fact that a man stabbed through the heart can so easily be brought back robs the MCU of real consequences. As a result, it's hard to worry too much about the likes of Captain America and Iron Man when even a lowly S.H.I.E.L.D. agent can be brought back from the dead. Coulson's death was shocking, and his return should simply never have happened if Marvel are expecting you to really invest in their characters and to actually worry about them.