Levi's Guidance Didn't Lead Eren Down a Path Toward Genocide:
I love how some people try to blame Levi for Eren ultimately choosing to do what he did with the Rumbling. I just saw someone claim that because of the advice Levi gave to Eren, and the mounting pressure being placed on his shoulders, that it formed an "ideology" in Eren that eventually led to him determining the Rumbling was the only course of action to be taken to save Paradis and his friends.
I know where they're getting this from. There's that moment during the RtS arc, after Eren manages to plug the hole in Wall Maria, when Levi tells him that their mission isn't over until all of their enemies are killed. This moment here:
They think this, along with Levi telling Eren to make whatever choice he can live with during the Female Titan arc, was central in Eren coming to the conclusion that he would have to wipe out all of humanity in order to safeguard the island and his friends.
The problem with this assessment, though, is that it assumes Eren actually believed the rest of humanity was really their enemies and that their extermination was necessary to protecting the people he loved. But we know Eren didn't actually believe that. When he arrives in Marley for the first time, and he looks around at all these people, he admits to himself that they aren't his enemies. That they're just regular people, like all of them were, back on Paradis the day Wall Maria fell.
This assessment further assumes that Eren's goal was to protect Paradis and his friends, which we know isn't true, because he admits the real reason to Ramzi, and then later Armin, which is that he wanted to do what he did in order to experience his idea of true freedom. The landscapes he saw in Armin's book, of an unexplored world devoid of humanity.
Jean as much as points out the lie of Eren's words, all the times leading up to this moment in which he'd claimed he was doing what he was doing to protect his loved ones:
Eren's idea of who the enemy was then was very simplistic. Titans were the enemy. Bertolt and Reiner were the enemy. That was it. The simplicity of this belief is reflected in how Eren swears to Reiner to one day kill him, right after Reiner kidnaps him. Through him repeatedly calling Reiner a "monster", dehumanizing him. But we see this simplistic idea of who their enemy is begin to shatter after they discover the truth of humanity beyond the Walls, when we see Eren's despondent demeanor at the ocean, when he asks if they kill all of their enemies on the other side of the sea, will they be free. And we see it shattered entirely when he has his encounter with Reiner, four years later, when Reiner reminds Eren of how he swore to kill him, and Eren half-heartedly recalls it, before admitting he no longer has any interest in that. This is Eren admitting that he understands now that Reiner was just like him, in the same position as he was. That he thought he was fighting a devil, just like Eren, and just like Eren knows he's going to do, Reiner also killed people after he understood they weren't really his enemy at all, weren't monsters or devils.
Claiming that Levi's advice to Eren is what pushed him toward committing the Rumbling requires one to believe that Eren committed the Rumbling while still holding the same, simplistic, black and white view of who their enemies were back when they retook Wall Maria. It requires one to believe that Eren still believes these people he's going to kill are inhuman monsters. That Eren doesn't know the people he's killing aren't his enemy at all. That Eren doesn't know they pose no threat to him.
But Eren does know those things. He absolutely knows.
What people don't seem to get about Eren's character is that all of his internal reasoning leading up to his triggering of the Rumbling is Eren trying desperately to convince himself that what he's doing is justified. He's seen the future. He's seen what he does. And so he tells himself all manner of lie to explain it away and save himself from the awful truth and the crushing guilt that comes with it.
He tells himself that he must have seen the future he did because they weren't able to find another solution. He tries to convince himself that he wouldn't have seen that specific future for any other reason. But then, Eren never gave the Survey Corps or anyone else a chance to even try to come up with another solution. He uses the hateful rhetoric spoken against the Paradisian Eldians as an excuse to move forward with his plan, but he'd already made that choice long before, had already schemed with Yelena and Floch and Zeke, long before they ever made it to Marley. Had already told Historia what his true intentions were, to betray Zeke and destroy all of humanity beyond the Walls. He was already decided on his course of action before they could ever travel to Marley to attempt negotiations. Again, it's just an excuse Eren tells himself and others to cope with his guilt and convince himself his actions are justified.
We see Eren's internal struggle once they arrive there because, as already pointed out, he realizes these people are just regular human beings, not monsters. He realizes they're all innocent and pose no threat to their lives. He's conscious of the fact that, just from the sheer numbers, it isn't justifiable to kill so many people to save so much fewer. He knows he's going to do it, but logically he can't see the reasoning, can't really convince himself that it's something that sits right with his heart. Still, he tries. He tries to convince himself that it isn't out of his own, evil desire, or out of some malicious intent, but that he's going to, as he says, "commit the greatest act of violence in history" because he just can't accept Zeke's plan of sterilizing the Eldian race, because it isn't a fair ending. He's trying to frame it to himself here as some act of righteousness. He goes through all of this, all of these rationalizations and excuses, before his breakdown with Ramzi and his confession of the truth.
He excuses his actions, right up to the very end, by telling himself and others that it's because of what he's been taught by example. This idea that he has to just keep "moving forward", parroting Hange's words back at Falco, and then again later, back at Hange. This idea that he has to "kill all of their enemies", like Levi told him during the mission to retake Maria. That he has to decide for himself, like Levi told him during the Female Titan arc.
But Eren committed the Rumbling, not to wipe out their enemies, not to keep moving forward, not to protect his friends or the island, but to fulfill his personal dream of freedom.
This wasn't a case of Eren misunderstanding Levi's advice, or even twisting it to fit his agenda or justify his actions. This wasn't a case of Eren forming an ideological mindset based off of Levi's words to him during the RtS arc.
You can't lay the blame for his actions at Levi's, or anyone else's feet, because Eren already well understood by the time he enacted the Rumbling, and even well before, that there was no justification for it. No excuse. No reasoning beyond his own, selfish desires. He wasn't driven toward it genuinely believing there was no other way.
Levi told Eren to make the choice he could live with, and in the end, Eren wound up doing the exact opposite. He made the choice that he knew could only and should only result in his own death.
He died with nothing but regret. It's why he breaks down like a pathetic child at the end, with Armin, and cries about not wanting to die, about wanting Mikasa to not move on from him. He doesn't feel fulfilled or unburdened by his choices. He doesn't feel at peace.
Because he knows he did the wrong thing, and he always knew he was doing the wrong thing. He wasn't lost in ideology. He wasn't confused about Levi's meaning, or Hange's meaning, or anyone else's meaning. He didn't misinterpret or misunderstand what they meant. He didn't get mixed up in the head from their words. He didn't get sent down the wrong path by their advice.
What he did was use their words and their advice to justify, both to himself and to others, what he already knew and had already decided he was going to do. He hid behind those things as a coping mechanism, to put a buffer between himself and the reality of what he was. To give himself a reason that made him feel like less of a monster, until finally he couldn't deny the truth anymore.
But Eren 100% knew what he was doing, and his choices were 100% on him.
He wasn't confused, or misguided. He didn't misunderstand anything. He understood perfectly well what Levi meant. What Hange meant. He understood perfectly well what the original purpose and ideals of the Survey Corps were and the ways in which they were now being perverted.
Floch and his fellow Yeagerists were lost in ideology. They misunderstood and misinterpreted. They twisted the original ideals of the SC to fit their agenda. They were sent down a bad path by Eren. But Eren always knew the truth. He never believed what he was doing was right or necessary.
Nobody made Eren the way he was, and nobody made Eren do what he did.
As he said to Zeke, as he said to Reiner, he was just born this way.