As we've all been primed to expect from the moment it was announced as the culmination of the first three Phases of the Marvel Cinematic Universe, Avengers: Infinity War (and its sequel) will leave things irreparably, infinitely different. The actors have talked up the threat as like nothing we've seen before, Kevin Feige has talked about fundamental changes to the way audiences experience the MCU and we're being promised a radically different approach to some of the movies they'll be making.
But we also have to consider at this point how different everything is going to be at the start of Infinity War, particularly from the last Avengers movie (and the last semi-Avengers movie, Civil War). Characters have undergone almighty development arcs (some on screen, some not), and already there are huge hints that some of the main cast are going to be hugely different.
In some cases, the changes might be purely cosmetic - though that usually means something in comic book movies (just as it will when Hawkeye becomes Ronin in Avengers 4) - while others have new (or improved) powers or emotional baggage or entirely new roles. In short, these are no longer the characters they once were. They're likely to be better and more complex (as characters tend to be when forced under greater threat), and that's absolutely not a bad thing.
So who will be the most unrecognisable from last time...