WARNING: The following contains spoilers for Season 4, Episode 10 of Attack on Titan, now streaming on Crunchyroll, FUNimation, Hulu and Amazon Prime.
Action shonen anime and manga often use power-scaling methods to make the main character gradually grow stronger to meet new challenges and overcome them. Countless classic examples can be found across the genre, but then there's Eren Yeager in Attack on Titan, who twists this idea into something monstrous.
Eren's power-scaling arc may be shonen power-scaling in its worst form. Not worst as in "badly done," but as in "intentionally concerning." Eren's friends and rivals are more concerned than encouraged by what they see happening to the once-heroic character.
How Eren Yeager Has Amassed Power So Far
At the series' start, Eren was an ordinary boy living in Shiganshina. Then the Titans arrived, and his father Grisha took some radical steps. Grisha took his son to a remote rural location and injected him with the Titan serum, then allowed Titan-Eren to eat him. This granted Eren the powers of the Founding Titan and the Attack Titan, though he wouldn't realize these powers for years. Instead, Eren trained to become a soldier alongside Mikasa, Armin, Sasha and others, preparing himself for anti-Titan combat.
Eren's first mission went very badly until he broke free with the Attack Titan and went on a rampage. Everyone feared and doubted his power at first, but Captain Levi argued in his defense and allowed Eren to take part in the next battle. There, Eren placed a massive boulder to seal off the wall's hole and fought against the Female Titan, Annie Leonhart, several times before he defeated and captured her.
By now, with all of Paradis Island free of the Titans, Eren and his friends know of the Marley Empire and the island's role in the world, and Eren took things to the next level. He's 100% confident in his use of the Attack Titan, using it to destroy incoming Marleyan ships before taking the fight to Marley on the empire's home turf. After storming the capital city in a fierce ambush, he dueled the War Hammer Titan before claiming her power as his own.
Eren now wields three Shifter Titans at once, and with contact with a royal-blood Titan, Eren can command Pure Titans at will. Like most protagonists in shonen, he has fought tooth and nail to get this far, but few training montages or "the power of friendship" moments have played a role. Instead, Eren's power-ups come through stockpiling Titan powers and using them as explosive ammo for his and Zeke's cunning plan.
The Terror Of Eren Yeager
At best, Eren's goals and methods can be described as brutal. He initially wanted to save the "last" human city and destroy all Titans, but he was mainly fueled by rage and vengeance, not a desire for peace. Now, his goals and methods have evolved in response to Zeke Yeager, the Marley Empire and Historia's rise as Paradis Island's queen. Eren is a pro-Eldia radical who, along with Zeke, aims to promote Eldia's position in the world at any bloody cost. Eren isn't becoming an idealistic hero, he's rapidly becoming a loose cannon, caring nothing for the costs of victory, and his power-scaling matches his attitude.
Eren now views Titans not as apocalyptic horrors, but as useful and patriotic weapons. Only Eldians can become Titans, so Eren views them as symbolic powerhouses that will destroy Eldia's enemies -- mainly the Marley Empire. To that end, Eren will use any Titan-related power to get ahead, including agreeing to Zeke's plan to use the mighty rumbling to scare the world with an army of Colossal Titans. The Nine Titans have become more like cool gadgets for Eren to collect, demonstrated by him gobbling up the War Hammer Titan as soon as he got a chance. (He tried to take the Jaw Titan, too.) Now, he's using that particular new power as a deterrent against anyone who would want to restrain him -- including his own allies.
It's clear that Eren is determined to do things his own way, regardless of the cost or collateral damage, and the earth-shuddering Titans are the key. The end justifies the means, in Eren's mind, and the world will fear his Titan powers, not admire them, ally and enemy alike. The power-ups shonen anime usually rewards its heroes with are being used for villainy.