WARNING: The following contains spoilers for Attack on Titan Season 4, Episode 28, "The Dawn of Humanity," now streaming on Funimation, Hulu and Crunchyroll.
Eren Jaeger has done some pretty terrible things in the Final Season of Attack on Titan and telling his foster sister, Mikasa Ackerman, that he's always hated her is easily the second-worst. The finale of The Final Season: Part Two included a flashback that added another layer of cruelty to Eren's harsh words for her by revealing that he was straight-up lying. Armin Arlert was certainly right for leaping across a table to assault Eren for hurting Mikasa, and it turned out he was right again in his belief that Eren made everything up when he berated them both.
Eren's whole thing in Attack on Titan is freedom -- freedom from Titans and freedom for Eldians. As a result of feeling like he's lived in a cage his whole life, he's developed an intense hatred for anyone who submits to oppression. After Eren padded his villainy stat sheet by slaughtering innocents in Marley and overthrowing Paradis Island's military via assassination and poisoning, he decided to cement his case for biggest jerk in the world by telling Mikasa he's always hated her. Mikasa had spent all her time in the Final Season up to that point defending Eren by saying he must be brainwashed by Zeke and Yelena, and her reward was a slap in the face from the person she loved most.
A good lie has a bit of truth mixed into it, and Eren used Mikasa's long history of sudden headaches to support his gaslighting. As a descendant of the Ackerman clan -- a group of warriors who protected the king by manifesting the power of Titans in human form -- Mikasa had an awakening of her power when Eren saved her from some crooks when they were kids. While it is true that Mikasa's power awakened in response to Eren's call to action, it was not because she'd mistaken him for her host that she's genetically hardwired to protect. Rather, it was because Eren inspired her and when he gave her his scarf, she devoted herself to him not out of compulsion, but love.
During that infamous table scene, Eren told Mikasa that her so-called compulsion to protect him makes her nothing more than a mindless slave with no will of her own. Eren's hatred for slavery is well known, so his alleged reason for hating Mikasa was very convincing, so much so that it brought Mikasa to tears and made the famously pacifistic Armin ready to throw hands. Eren even claimed that his half-brother, Zeke Jaeger, was the one who'd confirmed that Ackermans "activate" to defend their host. However, a flashback to the actual conversation revealed that Zeke said no such thing.
In fact, Zeke said the exact opposite of what Eren claimed he did in a brotherly heart-to-heart that was, tragically, all Zeke had ever wanted with Eren. When Eren voiced his insecurity about why Mikasa is so devoted to him as an Ackerman, Zeke told him that he'd never heard of this "activation to defend a host" thing Eren was going on about. What Zeke actually said was that it's more likely that Mikasa just likes Eren so much that she'll tear apart Titans for him. It's still unclear why Eren was out here just inventing mean things to say to people, but what's certain is that he's got a lot of apologies to make once the Rumbling is over -- assuming he or anyone else survives, that is.
The picture of why Eren has decided to destroy the entire world beyond Paradis Island is becoming clearer. However, it's not yet clear why telling Mikasa that he's always hated her was a necessary part of his plan. It's obviously not true, given he once tried to fistfight a Titan in his human form to protect her. Eren and Mikasa have always had a complex relationship as she played the role of his protector while he didn't like feeling inferior to her -- but to say that he's always hated her is just bogus. Hopefully, when Attack on Titan's Final Season: Part Three premieres in 2023, an explanation will be given for why Eren lied to Mikasa about having always hated her.
