Eren Yeager is one of the three main leads in the popular series attack on titan, he is the primary protagonist of the story, and given how he is portrayed it is no stretch to say that he is the most important character of the series becaue the series revolves around him and his decisions. Eren is a teenager who swears vengeance on the Titans who devoured his mother and devastated his town in Wall Maria's Shiganshina area. To battle the Titans, Eren enlists in the military and joins the Survey Corps, an elite organization of warriors that fight Titans outside the walls while simultaneously studying their physiology so they know what they're up against, but still, the elites struggle to defeat these titans no matter how good they are so basically it is suicide.
I can still remember that scene when they graduated even after years of watching the initial season and I still get goosebumps every time I remember the stakes that were given to them but still they chose to join the survey corp. It truly is a beautiful scene. In that scene, it was emphasized how truly powerful Eren's resolve was in defeating the titans, despite being overpowered by the opposing foe. Eren was always depicted as hardheaded, strong-willed, passionate, and impulsive, which are attributes of his strong determination to protect mankind and eventually escape the walls even as a kid and this scene shows it perfectly. However, this is only the start of Eren's character, later in the series, he will dive even greater lengths and uncover so much that his personality will change immensely.
In the arc struggle of Trost, Eren sacrificed himself for the life of Armin, within the span of a few minutes his entire squad was wiped out in their first mission. When a titan was approaching Armin Eren managed to save him from the titan's mouth, but that resulted in him being eaten instead. Luckily he managed to survive by unveiling a power within him, and that is becoming a titan himself, the being that he passionately hates. This self-sacrificial nature of him will later come to play in later parts of the series, and part this is what makes Eren such an interesting character to me, he is not like the other protagonist, he is not a sissy might be the term, he is driven by hatred and yet he doesn't fail to prioritize others before himself.
In the second season of attack on titan, a lot of revelations shocked the viewers. this is also why I liked season 2 a lot more than season 1. While season 1 focused on setting up the story, season 2 changed it so much that it is almost like a different anime. In this season it is found out that titans are actually human beings, and that they have been killing humans from the start. And a bigger revelation in the climax of the season is that Reiner and Bertholdt, a close friend of Eren turned out to be the instigators of the death of the mother of Eren and the cause of the destruction of his city. It is then made clear that Eren will kill anybody that opposes his belief and ideals even the people who spent time with him as a friend. He is put in a dilemma but he didn't waver and almost managed to kill Reiner.
In season 3 we manage to see a face of Eren that is not usually seen. When you look at Eren, the only thing you see is a layer of rage. You witness him lose a few battles and assume he's weak for requiring assistance. Eren is aware that his father has entrusted him with those abilities. He's a young man, a typical young man who carries a great deal of load on his shoulders. He admits that he is an ordinary person. And in this season he is given doubt, doubt that maybe his father is in the wrong and maybe the founding titan powers is not meant for him. This results in him breaking down and submitting to getting eaten by Historia without fighting. Eren was always depicted as hardheaded, strong-willed, passionate, and impulsive but it is shown here that he is insecure and unsure as well. This is soon resolved in my most beloved episode of the series Attack on Titan Season 3 Episode 11 The Bystander.
THIS LAST PART CONTAINS MANGA SPOILER!!!
For Eren, everyone is born free and should remain so, so don't let anyone take that away from you. Fight for your freedom, and if you don't fight back against whatever is robbing you of it, you'll lose it. To put it another way, you become a slave. Eren's primary purpose is to protect the people within the walls, and he believes that if he can eradicate all external dangers, Paradis will be safe for future generations. Eren reveals that he turned the bad guy so that he could make Armin and the alliance the heroes who saved humanity from extinction by stopping him. To put it another way, he desired to die at the hands of his buddies in order to ensure their liberty. For their sake, he gave up his life and liberty.
Some people do not like this ending, but for me it is beautiful, it is a bitter ending that makes you think about how pure he once was. True it was not as climactic compared to other parts of the series, but personally, I like how it ended in such an anti-climactic way. You can also connect it to how people never really knew what Eren did. He will forever be marked as the villain in history despite being the real hero, not the purest hero because he did intend to kill everyone as well, but still, he was a hero of Paradis. If you think about it that way it is also anti-climactic to a degree. I think Isayama made a masterpiece through and through, and Eren being the main character of the masterpiece, is a masterpiece of a character as well, It just shows how human he is, making mistakes and sometimes the worst decision you can think about but still, he is an amazing character. In conclusion, Eren may not have the purest heart or the strongest power, he only has his will and his friends to back him up, he may not be THE perfect person but for me, he is THE perfect protagonist of a series like Attack on Titan.