Attack on Titan (or, as its Japanese name actually means, "Advancing Giants") is an anime with the premise that 100 years ago, a pseudo-medieval human race was beset by the "Titans": enormous human bodies with the intelligence you'd expect from a slime in a fantasy RPG, but incredible strength, rapid healing of any wounds, and an insatiable hunger for human blood. Unable to win the war, the humans managed to construct three massive walls and retreat behind them. Now, after 100 years, a unique titan appears and breaks a hole in the outermost wall. The human soldiers are armed with special maneuvering gear that allows them to essentially fly in a Spider Man-like manner, swords, and the knowledge of an extremely precise weakpoint on the Titan's body that allows you to actually kill it.
The show has a strong protagonist, very strong emotional impact, and a good soundtrack. However, I would not recommend it, due to the following criticisms:
The outrageous misandry in the first two episodes. In episode 1, Eren (the protagonist) does something a bit reckless and that many would consider overzealous but that was actually a heroic deed of justice, and Mikasa (his adopted sister) drags him away and throws him into a wall for it. It's bad enough that he was completely helpless as she dragged him down an entire alley (they're the same age!), but then he doesn't even retaliate, or even seem very angry at her for what was clearly an act of unprovoked violence. This is not just sexism, it is bad writing because it's out of character for both of them. Mikasa is supposed to be calm, reserved, and protective toward Eren, not physically abusive. Eren, on the other hand, is a pugnacious, reckless boy who loves to fight for justice like he demonstrates several times early on in the series. He does not come off as the polite-mannered type who wouldn't hit a girl back if she hit him first.
It gets even worse in the next episode. Here Eren is yelling at Armin for despairing, and Mikasa punches him in the head. He falls over and cries. Then she force feeds him the bread Armin got for them that he said he wouldn't eat because other people needed it more. And this is portrayed as acceptable! Nobody would have tolerated either of these scenes if they had been a male character lashing out in violence against a female character, especially not the second one. Both of them are instances both of outrageous misandry and of terrible, out-of-character writing.
I read some more in the manga after I finished season 1 (the anime was just the first season back then), and it seems like the misandry picks back up after a while (a scene where Mikasa won't even let Eren help carry things because he "might get tired"). That was what finally led me to drop it. And sure, you could argue Mikasa was obviously making a joke, but that's completely out of character for her, and besides, it was obvious it was really offending Eren.
Eren is the most severely under-glorified character I've ever seen. It's just awful. He's an outright male damsel in distresss. When he isn't captured (which I'd estimate to be half the source material consumption time), he's either losing a fight, doing nothing, or using his unique power that no one else has and that has absolutely nothing to do with the five years he spent in training. (The power is to turn into a titan himself). And that still usually ends with him going back to being captured. This is especially bad because Eren is the type of character who really deserves agency and competence more than any other character, even more than any other protagonist. He has top marks in ambition, endurance and courage, and so it's incredibly unsatisfying that the writer doesn't give him an ounce of credit, ever.
After where the first season of the anime ended, the story just gradually went to shit. It died a slow and painful death. Aborted foreshadowing, positive portrayal of monarchy, using a flashback to avoid telling the audience what the POV characters knew until after it mattered, raising more and more mysteries without answering any, and going so long without mentioning the final enemy of season 1 (who was never killed) that I literally forgot she existed.
Despite all these horrible flaws that make it not worth watching overall, there's a lot writers can learn from Attack On Titan. For one thing, it contains a great example of the dignified rescue approach that I wrote about in one of my first articles. This is the flashback in episode 6 or so that explains how Eren and Mikasa met. When they were little (I think their age was stated but I don't remember it), Mikasa's parents were killed and she was kidnapped by three human traffickers or whatever. Eren and his father found the scene. His father calls the police, but Eren decides they won't arrive in time and runs off after Mikasa himself. He finds the murderers and, instead of magically outfighting them despite his inferior size and numbers, he picks off two of them using clever tactics and deception, then thinks that's all of them, enters the room and unties Mikasa, but as soon as she speaks the third one comes back and pins Eren to the wall, choking him to death. Mikasa picks up a knife and stabs the remaining enemy to death, returning the save. Not only did it succeed in not damselizing Mikasa, the scene showed us the origin of her modern-day personality. In the scene, she hesitates to take action until Eren prompts with "If you don't fight, you can't win" (a piece of advice that she looks back to for motivation later), showing that at that time she was a submissive person just like how you'd expect a damsel in distress to be, but the experience changed her in a very believable way. She lost both her parents that day. Eren, being her savior, naturally became the most important person to her, and she tries very hard to protect him after that, event to the extent of wanting him to be a coward: before the battle for Trost, where they are sent to opposite sides of the city by their commanders, she tells him if the battle gets chaotic, "Come find me, I'll protect you!".
Besides that beautiful scene, the first season of the anime was just really powerful. They did a great job portraying the fear of battle (unlike Star Wars) and how much the stress grates on the minds of soldiers. A particularly glorious scene was in the battle for Trost, after half of Eren's team is crushed or eaten alive by the first Titans they meet, including Eren himself (or so they believe). Mikasa arrives on the scene and finds the rest of them hiding on top of a building sulking in despair. She gives a motivational speech and gets them all back on their feet. Amplified by the music it plays, I don't know if it's possible to watch that scene and not at least get goosebumps.
Another great instance of emotional tension was in the forest of tall trees (yes, it's called that). This is after Eren and the others join the scout regiment, a branch of the military that ventures outside human territory to gather information and maybe pick off some titans without risking civilian lives. They are chased into the forest by a special titan with extreme intelligence and skill. Their orders are to ignore their comrades being picked off by the titan and keep leading it deeper into the forest, following a plan that their leader hasn't explained to his troops (not because he doesn't think his comrades deserve to know, but because he suspects there's a traitor in their ranks, and he's right). In this situation, Eren must choose between trusting the commander or stopping to confront the titan. Levi (a soldier between Eren and the commander in rank) even tells him that both choices are reasonable. Surpsinigly, Eren chooses to trust the commander, but the plan ends in disaster, with Levi's entire squad being killed, and so after that Eren tries to take back his choice and confront the special titan using his titan transformation powers, but he loses the fistfight and the situation turns out even worse because he tried to reverse his decision. Imagine the guilt. Not to mention the scene succeeded in a very rare feat - giving the hero a choice and portraying both options as reasonable.
Yet another instance is the scene inside the innermost wall where Eren and co. lead one of their friends that trained with them into a trap, suspecting that she is the traitor. They turn out to be right, but she turns into the special titan from the forest before their trap is quite ready, and when Eren tries to transform to fight her (which involves biting his own hand so hard that it bleeds profusely), it at first doesn't work. He ends up trying it a second time, mutilating himself to a horrifying extent, and it works. What I wanted to praise about the scene was the way it used extreme gore in an entirely called-for way. Most of the time I find extreme gore scenes a bit difficult to watch, and this was no exception, only it was a good thing. It was like Sayori's death scene from Doki Doki Literature Club.