The main problem with this show is that its pacing is way too fast. It needed at least 20 episodes, ideally closer to 25, as they were far too ambitious for only 13.
I think episode 10 best illustrates the potential Angel Beats would've had with a longer run time. Helping people come to terms with the unfair circumstances of their deaths so they can leave the school-life purgatory could've been amazing if it had more room to breathe, but instead we got one pretty solid episode and then a massive rush-job to get the hundreds of other students to let go by having it happen off-screen.
Speaking of characters, there are way too many and most of them have little to no personality beyond one or two basic traits that are used solely for comedic effect. There was no time to devote to them because the writers had to squeeze this massive cast into such a short runtime. For most of them, I can recall a handful of memorable scenes like ninja girl dying to save a toy dog or when glasses guy took his shirt off in class and flexed his muscles to distract everyone, but I don't remember much beyond that. I certainly don't remember their names, except TK because it's just two letters. It's hard to forget something so simple. Either cut down on the characters or make the show longer to give them the time they need, otherwise I won't care about them.
Another problem with the pacing was how every time a major new problem was introduced that seemed like it could've made for an entire story arc (the new Student Counsel President and the shadow monsters especially stand out), it was usually resolved in the next episode or two. The abrupt spikes in tension and release are very jarring and unsatisfying.
Yuri and Kanade's early interactions should've been shown. Yuri's spent the entire series trying to stop her from obliterating people, but then she abruptly changes her mind when the situation is laid out for her. What did Kanade say when they first met? Just how badly did she have to screw up to make Yuri hostile enough to want to forge guns and attempt to kill her? She must've said something incomprehensibly stupid for an entire resistance organization to form with a massive underground weapon manufacturing system set up for the sole purpose to stopping her from doing something that's ultimately beneficial for them. I can believe that someone as stiff and unsociable as Kanade could make a bad first impression, but I don't know how she could mess it up THAT hard.
On the subject of Kanade, her sudden personality shift in the last episode was strange and incredibly out of character. She was so robot-like up until then, only showing small glimpses of humanity beneath her stoic demeanor, but all of a sudden she's expressing regular emotions and acting kawaii for no reason. She showed no prior inclination towards such an attitude before the final episode. That wasn't a Character Arc, it was a Character Right-Angle. It takes a LOT for a person to change that much, and even if she's finally expressing what she's always felt, people don't change the way they express themselves that abruptly. This is something I can personally relate to, as I'm not an emotive person. My voice is monotone, and my expressions are incredibly subdued. The people who know me would notice if I suddenly started expressing my feelings the way Kanade suddenly does.
Otonashi and Kanade's "relationship" was handled clumsily to put it lightly. I could've believed it was the start of a potential romance, but Otonashi suddenly insists that he loves her and begs her not to leave him as if they've known each other for a very long time. I've never liked the trope of characters falling for each other after only knowing one another for a relatively short period of time, but I could've excused it if there were any hint of them having some kind of connection like that. I never got the impression that there was something romantic going on, even after watching the show a 2nd time and knowing where it was going.
If Kanade has his heart, how is it that Otonashi arrived in the purgatory world AFTER her? She had clearly been there for a long time if she had set up the whole Angel system to give herself powers (how did she do that, by the way?). It's incredibly contrived to say that the purgatory world has weird non-linear time whatever or that Otonashi was sent into the future after Kanade died. And given how young Kanade seems to be, his heart clearly didn't extend her life very far. Sure, living a few years more is better than dying as a child, but it would've been more impactful if someone got his donated organs and lived a long fulfilling life. Kanade dying young makes his death feel almost pointless because the person he helped didn't get to live very long either. Or were they trying to imply that Kanade DID living a full life and that she was sent back in time to the purgatory world and reverse-aged to when she got the transplant so she could meet the guy who saved her? Does something like this happen to EVERY organ donor? Why didn't he meet the people who got his other donated organs? What makes him and Kanade so special? If she did get sent back in time, why did it send her so far back before he got there and why does she not tell Otonashi why she's there at all? She said she figured it out in episode one when she stabbed him and didn't feel his heart. Why is his heart even missing if this purgatory world isn't the same as the normal world? Why is he only missing his heart when he donated his other organs? If his body in this world is meant to mirror his body in the real world, shouldn't he have surgical marks all over him from when his organs were removed?
Maybe Kanade is still alive and she was sent to the purgatory world to meet him? If that is the case why, how, and what makes those two so special that this would happen at all? I don't know what the explanation is, but no matter the case, it's extremely contrived, if not an outright plot hole.
Who was that guy in the room with all of the monitors that Yuri confronts near the end of the series? I get that his purpose in the plot was to prevent people from staying in the purgatory school world indefinitely (or am I misremembering? I think it was something about love being bad because it would make people want to stay) but it's really strange to introduce a new villain in the penultimate episode and then defeat him 3 minutes later. It would've been better if he had been an established character with an actual name, someone we might have some kind of connection to in any way whatsoever. Even if he were a minor background character, at least recognizing his existence would be better than pulling him out of the ether to serve the plot.
The show isn't very good. It's not terrible, and I enjoyed watching it, but it's quite flawed.
