Considering the amount of time, effort and money that Marvel had invested in telling the background of characters through their own movies, as well as building up this overarching plot by weaving story points into different films, The Avengers takes quite a long time to get going. This is not to say that the first half of the film was unnecessary, but it was surprising that given the number of heroes involved, we did not really see any action until the Helicarrier was attacked midway through the film. This was the tipping point, and everything before this seemed pretty slow. We saw Iron Man fixing a pipe and flying around New York, and we saw a pretty underwhelming car chase, but most of the exciting scenes and iconic moments were from the final half - Agent Coulsons sacrifice, the Hulk battling the Chitauri and the iconic scene where the Avengers stand preparing to defend New York City all happen towards the end.