Pretty much every other review says that the ending sucks, and that the beginning is better. However, I disagree, and let me explain.

This review tries hard to avoid spoilers.
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I think the biggest reason people are disappointed is because this anime isn't just an action anime. It's not just cyberpunk dystopia glamorizing bad boys. Sure, it starts that way, but then halfway the mask comes off and you see the true form of the anime.

The anime's true form is about the collapse of a dystopian society; the darkness that was hidden just below the surface, ready to explode at a hair-trigger. It's a poetic tragedy, and it dares to end in a way very contrary to most anime.

The first half is more of a standard action cyberpunk shounen anime, but it goes a good job of showing how broken the world of Akudama Drive really is. The focus is about the invasion on the train and the delivery of the vault contents, but the groundwork is laid for much more sinister things. But these things aren't important yet, as they are background elements. So instead, we get character introductions, a lot of action and fighting scenes, and your generic ragtag-group of misfits working towards a common goal.

But that's just it. That's the start. The prologue, if you will. Because these events set up the things to follow. This anime is about cause and effect. The cause being the attack on the shinkansen to rescue the vault, and the effects having huge consequences on the very world they're in itself, and these cause and effect chains end up spiraling out of control in the second half of the anime.

And yet, the goal in the second half is still the same as the first, that being to deliver the vault contents the target destination. That destination might have changed, and the characters might need new motivation to do it, but that's the whole point of what the anime is focusing on. That's the mission the protagonists have, and that's the story the anime will continue to tell, regardless of what else happens.

This is where the anime shines brilliantly. The entire anime's development and worldbuilding and progression remains in the background. The protagonists' actions have massive consequences, but those consequences aren't the focus of the plot. The consequences affect the plot and are important, but aren't the focus, and thus aren't resolved. The goal is to finish the delivery, and only then does the anime end, at all costs.

It's true, that there are handwaves and plot-holes. But as far as I can tell, none of those matter. The anime glosses over things sometimes, but those things aren't relevant to the story. Do we need to know how they got back to the city after robbing the vault? Not really. What's important is that they did. Is the reason Kanto wants the vault contents really stupid? Yes it is, but does it matter? No, because we still don't want them to have it. Are the deus-ex-machina's overly convenient? Yes, but who cares if it removes the need to waste time on mundane things. Overall, despite being very bothered by the handwaves at the start, by the end I wasn't bothered at all because of how clean the anime's focus was. It never lost track of the one story it wanted to tell, and didn't waste time with unnecessary moments.

This anime is a daring, poetic tragedy that tells a story, just not the one you initially think it is. Very few anime have a well-written unhappy ending, and this is one of them. Sometimes, there are no winners, and sometimes, things just happen.