Things start off promisingly enough. You'll hear a lot about the opening sequence of the film, and for good reason: it's an incredible piece of action filmmaking, staged as a single shot with one of the most triumphant reveals I've ever seen in this kind of movie. It's downright anthemic — but it also sets a bar the movie is never able to clear again. Instead, the team soon find themselves facing off against the titular Ultron. Voiced by James Spader, Ultron is an accidental bastard; the result of Tony Stark's tech wizardry melding with an alien artifact, and he takes the form of a wisecracking robot with very little respect for authority. He also thinks destroying humanity is the best way to establish world peace, which the film never really explains the logic behind, but let's be real — movies have tried to sell us much more outlandish plots and have gotten away with it just fine.

The opening sequence is an incredible piece of action filmmaking

But between Ultron's lame jokes and general lack of motivation, he never manages to become a villain you can take seriously. It's a depressingly bland dynamic compared to the fun Tom Hiddleston had as Loki in the first film, but thankfully Ultron has some backup in the form of a pair of twins (Aaron Taylor-Johnson and Elizabeth Olsen) who have some special powers of their own.

What’s shocking is how so many things that were strengths in the first film fall flat here. Whedon hits his chatty stride early on as the team hangs out and ribs each other during a party, and it’s filled with some signature character bits. But given the events of the last few films in the series, the lightheartedness feels strangely out of place. The moral confusion Captain America went through in Winter Soldier is nowhere to be seen. Tony Stark is yucking it up despite the journey of self-doubt he took in Iron Man 3. Thor... well, Thor’s always exactly the same, but even if he wasn't, it’s hard to take any of the interactions seriously when they all seem pulled from some superhero sitcom that just reset itself the previous week. To sell the idea of a massive, ongoing story, Marvel needs to keep its character development as consistent as it keeps its mythology.