2. Loki - The Avengers
Tom Hiddleston's Loki is an extremely fun villain to watch, and The Avengers was a totally wild ride, but that doesn't excuse how needlessly convoluted his plan was. Loki ends up getting caught by The Avengers, and they remark the considerable ease with which they managed to achieve this, instantly becoming suspicious that he might have a plan, and they're right to feel this way. From here, Loki's back-up arrives, firing at the Helicarrier, which in turn triggers Bruce Banner's transformation into The Hulk, and in turn the Helicarrier suffers catastrophic damage. Given what little agency Loki has in this fight, what was the point of him getting himself caught in the first place? Why not scramble attack jets remotely and have Banner Hulk out all on his own? That'd probably cause some pretty substantial damage without taking the risk of exposing himself so brazenly. Plus, given that we know Loki is just answering to an even greater power, it all seems a bit redundant in the end. Furthermore, Internet rumour has speculated that this is all just part of yet
another aspect of Loki's plan, that he intends to return to Asgard to wreak havoc in some form or another. We'll have to wait and see how that pans out...