7. Thor Brings The Hammer Down (Thor)
Thor starts off as a narcissistic prince who's had everything handed to him his whole life and never faced defeat or humility; therefore, he thinks he can do no wrong and listens to no one. Call him the Barack Obama of the Asgardian world. After angering his father Odin by leading an unauthorized assault against the Frost Giants (and while it's debatable if Frost Giants can be "innocent", they certainly weren't the aggressors, either), potentially starting a war, Odin banishes him to Earth minus his godlike powers and mighty Mjolnir to learn humility. Which he does by getting drunk with one scientist and flirting shamelessly with another in the form of Natalie Portman, who is about as believable as a genius scientist as Jessica Alba was playing Sue Storm in the Fantastic Four. I'm not really sure how he learns humility by doing any of that, but apparently he does to the point that when Loki sends The Destroyer to finish off Thor once and for all, he "sacrifices" himself...only to have Mjolnir resurrect him and restore his powers.
Sounds like a great tale of redemption, doesn't it? Except for the fact The Destroyer appears to kill several SHIELD agents when he shows up and subsequently also lays waste to more than one building in the small town where Thor's been hanging out. There's no doubt at least some people were probably hiding inside those buildings cowering in fear. Although it's also never implicitly shown...well, Thor creates a tornado to get rid of The Destroyer and generally us mortal folk die in tornadoes. Maybe just grabbing The Destroyer and flying into the sky with him--or better yet, to the countless miles of uninhabited desert around them--would have been a better idea than creating a twister that sucked up every mortal in its wake. Which circles back to the whole chain of events being started simply because Thor was a narcissistic prick who wouldn't listen to anyone.