Erwin's character was always one shrouded in a thin veil of mystery. In the first two seasons, he was a cut-throat leader who would do anything to achieve his ambitions, but there was one problem. What were his ambitions? Season three showed us a glimpse into that with the loss of his father due to an innocent interest in the outside world. His goals in discovering the truths of the world are set, and we move into season 3 part 2, where he has to make the ultimate decision. To die as the leader he feigned to be all this time or to realize his dream to the detriment of all of those around him. Erwin said it best himself, the recruits never would agree to the charge if Erwin was not at the helm. If they were to do nothing though, they would die, as would humanity within the walls. In his agony, the person closest to him gave the final answer on what he should do. Levi asked him to give up on his dreams and die. Erwin was to walk into hell so that others could fulfill his ambitions as they walked towards the future. That was the end of Erwin at that moment. Once his final speech was given, the instant he hopped on that horse, Erwin had resigned himself to death. The reason Levi in the end decided to use the shot on Armin was that Erwin had given up on his dream, and therefore had no force to drive him forward. Kenny's words, saying that everyone's drunk on something was meant for this moment. Erwin put down his drink, and even if he hadn't all he looked forward to was the basement. Even if he had lived, what would drive him forward after that? There was no guarantee that Erwin would be the same leader if he lost his drive, and so Levi picked the one he thought could become the next Erwin, even if he wasn't able to replace him at that moment.
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Armin
Armin came a long way from where he was in season one. He screamed on the rooftops as he saw his comrades being eaten, giving up without putting up any sort of fight. He could use his head but relied heavily on others to take action for him. He started this season by showing how he progressed, taking command and smoking out Reiner from the walls. He regressed, however, once his plan to keep Bertolt in check failed. He tried to pass off the responsibility of leading to Jean. Jean was able to keep his cool, but he reminded Armin that he could only take them so far and that Armin himself would need to assume command again at some point. Armin eventually realized the quirk when it comes to the Colossal titan's steam, and his heroic plan was set in motion. Whether or not Armin truly intended to die beforehand isn't something we'll probably ever know. Maybe he lied to Eren, or maybe partway through the plan, he realized that they desperately needed the time. Regardless, he left everything in Eren's hands, almost like he tried to shift things to Jean, but the difference is the context. This was done out of courage, not cowardice. Armin's pure ambition is why he was revived by Levi, he had dreams yet to realize, far off in the distance, as opposed to Erwin, whose dreams were so close. They were similar men, both driven by dreams.
Art
I don't think there's much you can do to hate on the job that WIT Studio did with Attack on Titan. The single blemish on the entirety of the art side of things would probably be the CGI Colossal titan, but this was back in 2019, and WIT Studio is only so big and can likely only afford to do so much. They did at least fully animate the titan whenever it was something important, like when Eren finally took down Bertolt. The general animation is the shining star though. Everything WIT does is rather great, but they put a lot of love into Attack on Titan. The background is carefully crafted, the fights are fluid, and the art style they made for the anime fits the scenes they craft. It was pure consistency.
The OST is one of the best in anime, or at the very least, one of the most iconic. The director did a great job in using the music as well to maximize intensity and emotion in every scene. I still get goosebumps at the end of episode one while the stage gets set for the season with the appearance of all the titans.
Entertainment Value
There are rarely dull moments in Attack on Titan, and there's not a single one in this season. The fights are all engaging, from enemy versus enemy to friend versus friend. The clean animation in the fights as well makes it so that your eyes are able to focus entirely on what's happening at the moment, and your brain doesn't go astray. You'd be hard-pressed to be distracted during any of them. The scenes of worldbuilding draw you in as well. The secret of the basement is so simple yet so intriguing as it blows away everything we thought we knew and explodes the world wide open. Grisha's POV was also very interesting to see.
Mystery and Intrigue Culminate into Emotion
The mysteries of Attack on Titan all lead to this moment as a vast majority of the world is revealed to the viewer through the eyes of Grisha, while more is set up during the fight and during those Grisha flashbacks. I don't think any other season of Attack on Titan can compare, even if they all have their fair share of mystery involved. The greatest thing this anime does though take its mysteries and invest emotion behind them. With the reveal of the basement, we didn't have Erwin there to share in the reveal as he so desperately wanted, we had the emotion of Eren and Mikasa returning to the home they lost. Learning Grisha's past hurts the viewer. Emotion is invested even into the enemies. We only know so much about their reasons why, but we know that they have them. The most important of the emotional moments the mysteries brought us to would be the beach scene. I think the beach scene might just be one of the greatest single scenes in all forms of media, let alone anime. There's so much emotion as the future Eren fought so hard to fight for is shown to be even more out of reach. They had to fight so hard just to learn that the entire world is against them and that there was no other option but to fight. He has to ask the question, "If we kill all of our enemies on the other side of the ocean, will we finally be free?" That final moment of despair leaves us in a state of thinking. We sit back and revel in that same line of thinking, wondering if there will ever be peace for our characters.
Conclusion
WIT Studio may have been unable to continue Attack on Titan past this season, but they didn't leave it as a pile of ash, they wrote a love letter to the series. As we leave with that beautiful ocean OST, so do they. All of their emotions are packed into ten world-breaking episodes. Seldom will you be able to find a series with as much impact as Attack on Titan has. The series as a whole may not be perfect, whatever feelings you had about season one, or even the end of the manga as a whole is entirely valid, but this is a review of this part of Attack on Titan. Season 3 Part 2 is about as close to perfection as it gets.