--Tony Stark, Avengers: Endgame
"I will shred this universe down to its last atom . . ."
--Thanos, Avengers: Endgame
If you have not seen Endgame and do not want the movie to be spoiled, do not read any further. There are many spoilers below!
Endgame has several fairly major conceptual or execution-based flaws, but the depth of the characterization, not to mention the unprecedented stakes and cultural significance, far outweighs any of the asinine elements. Having already detailed the broad successes and blunders of the film, I want to focus on the specifics here. From the (irrational and therefore incorrect) in-movie analysis of time in quantum physics to the unprecedented scale of the final battle to the largely excellent use of established characters, much of Endgame's content deserves a second review--this time with major spoilers. Since there is so much to dissect, this will easily be the longest review I have written.
This section will mostly focus on how the characters are handled, not on special effects and acting, as I already addressed those aspects of the film in my non-spoiler review.
Returning as the grand villain, Thanos is far more sadistic and malevolent in Endgame than he was in Infinity War, yet there are no new revelations about his backstory or worldview. I hoped that more about his motivations would come to light--perhaps he would even be attempting to save the universe from a being that consumes life forms, like Galactus--but the Thanos of Endgame would hardly be anything spectacular apart from the character development in the previous Avengers movie. Without Infinity War, this Thanos is just another expendable, generic MCU villain, albeit one that is far more imposing and powerful than the others.
Now for the protagonists! Since some characters are finally developed in ways that don't relegate them to the background or sidelines of the MCU, I will start with them. Hawkeye finally receives enough attention to make him a deep character, though the Ronin subplot (where Hawkeye becomes a vigilante) is rushed and somewhat out of place. Yes, it gives Hawkeye a reason to suggest that he has committed wrongs that he needs to atone for in the scene with him and Black Widow on Vormir, but there was almost no space in the runtime to actually explore the Ronin identity in any thorough way.
However, his platonic but passionate friendship with Black Widow, which is only made more significant due to him having been married for the majority of the time the friendship has existed for, forms the emotional foundation of a key death scene. Black Widow's death gives her the opportunity to become one of the only women in cinema to sacrifice herself for a cosmic purpose, and this should not be trivialized. Thankfully, there have been some great opposite gender friendships in cinema (like Marlin and Dory's relationship), but rarely, if ever, does a female character get the chance to sacrifice herself for a male friend or for the sake of the universe as a whole. If nothing else, Black Widow's death is meaningful for this reason alone.
In fact, the women of the MCU are often at their best in Endgame, with one scene even giving a nod to A-Force (many scenes have done this with men and received no backlash, but, of course, some people criticize the A-Force tease). Black Widow is far from the only female character to have great moments; Nebula, Pepper, and Captain Marvel, to provide several examples, also have some great scenes of their own. Captain Marvel is used sparingly, but her scenes are very well-placed--she does not singhandedly defeat Thanos, but simply having her buy time for Tony (knowingly or unknowingly) as she holds Thanos' fingers apart while he tries to snap again was an effective way to signal that she will be the face of the MCU going forward.
As for Thor, the script takes him in a fairly unpredictable direction that, at first, is very out of place in a story that needed a consistent gravity. Thor's alcoholism, responsible for him becoming overweight, still does not stop Chris Hemsworth from delivering an excellent performance that contains both comedy and personal vulnerability. Because of Hemsworth, Thor remains a fantastic character despite the unexpected changes to his body.
Though there are so many great characters or character moments left to address, the two most important characters that have yet to be mentioned are Captain America and Iron Man. Both are handled very well in Endgame, with Steve's arc ending with the opportunity for him to finally live a fulfilling life with Peggy and Tony's ending with his sacrificial use of the infinity stones to vaporize Thanos and his legions. It would have been very difficult for the writers to give either character a more fitting ending, and the growth of both characters throughout the MCU is on full display even before their final scenes. It would be very easy for some people to literally experience the conclusions to the arcs for Steve and Tony as if they have in some way lost actual friends.
Story
The first third of the movie is very slow in some ways, but it does portray the emptiness and despair that even the Avengers experience after Thanos' genocidal snap. Captain Marvel rescues Tony and Nebula, and Nebula reveals the likely location of Thanos. Within the first ten minutes, Thor beheads Thanos, leaving the vast majority of the three hour runtime to show subsequent events. After a five year leap forward, Ant-Man exits the quantum realm, Hawkeye hunts down crime lords as Ronin, and Bruce Banner celebrates the merging of his "normal" mind with the Hulk's body.
As the remaining Avengers handle their grief in various ways, with some even having the luxury of fulfilling lives, Ant-Man proposes a "time heist" that involves using the quantum world to travel to the past, retrieving the infinity stones before Thanos snaps, and resurrecting all of the beings killed by the snap. Time travel allows for very clever nostalgic moments to be included all throughout the second act of the movie, though at least one scene seemingly alludes to a recent comic that has nothing to do with the MCU (Captain America's "Hail Hydra" moment). The recovery of the time stones leads to a massive battle when the snap is reversed and the Thanos of the past is brought to the present, with the fight's scale easily surpassing that of any battle sequence from Game of Thrones. The fight only ends when Iron Man uses the infinity stones to snap Thanos out of existence, and the power of the stones ultimately kills him.
Intellectual Content
Endgame tries to shoehorn quantum physics into the storyline, with Ant-Man claiming that time passes differently in the quantum realm (he says five hours passed while he was in the quantum realm and five years passed at the macro scale). However, his claim is erroneous. The experience or perception of time can differ from person to person or place to place, but five hours can only be five hours and five years only five years, no matter what Ant-Man says. Only his experience with chronoception could differ from that of other people.
That matter behaves differently on the quantum scale does not mean that time does as well. Time is immaterial, while matter is, of course, physical; events in the material world cannot take place without time, but time could exist independently of matter. This means that changes to the behavior of matter do not necessitate changes in the flow of time. Of course, a specific amount of time cannot actually pass at different speeds, so no discovery in quantum physics can contradict logical truths such as this.
Conclusion
Endgame's flaws do not prevent it from being by far the most epic and emotionally powerful superhero movie that will perhaps ever be crafted. An unprecedented level of attention to detail permeates most of the film: Endgame concludes a 20+ film story arc, and it does so while providing dozens of well-integrated callbacks to earlier movies. It has its issues, but there may never again be a movie with such a degree of franchise and even broad cultural significance. Anyone who loves the characters of the MCU will almost certainly adore Endgame for the way that it affirms their best parts. If there is one movie to see in theaters this year, Endgame is very likely that movie.