Originally Posted by DrCosmic
It's much more risky, because instead of setting the expectation of incomplete stories from the beginning and promising a payoff at a certain time, like LOTR did, you're disappointed the audience whose come to expect payoff from each of the Marvel Studios films, and indeed, from the Thor franchise. It'd be like the Matrix. The first one was self contained, the second one wasn't, and everyone was pissed.
It's important to note the difference between defeating a bad guy and defeating a bad guy's "scheme"
The Avengers don't have to kill Thanos in A2 to conclude the movie