like i don't get the hate eren garnered with the ending at all, again i never kept up with the fandom and don't remember why exactly he got people turn on him left and right and say that his character is ruined etc just the overall atmosphere, and lots of people being angry... but i don't think that anything they said is supported by the narrative
eren has been born crazy (something he admitted) but besides that he just had a lot of anger as an angsty teenager (poked fun at with hange calling him out on it twice) and his choices were selfish because, well... it's one of the themes of this work... there's selfishness hidden in all selfless causes, it's up to the individual what choices they make and why... eren was a cornered animal that hated and lashed out at the world, he put his own feelings before reason because he's just a regular person who is not extraordinary or particularly noble. it's actually brought up on different occasions, reiner saying twice that eren is the worst person in the world to be entrusted with that power, and in the end eren flat out admitting that he's just a regular person ("an idiot") that so happened to gain god-like powers. in this respect he was like ymir the founder (also addressed in the story.), two kids shaped by their circumstances who were made into forces beyond nature by pure happening.
in the end though did he get to have his cake and eat it too, or did he get the worse halves of both worlds? the outside world hated him, and he hated it back. ironically, him deciding to trample it validated its hatred towards eldians and confirmed its greatest fears. he wiped out 80% of people both because he was angry at the injustice it treated his people with, and because he wanted to realize his own old fantasy of the world beyond the walls being a blank slate his to explore.
but he did also want to save ymir the founder, to save his friends, and to save paradis. he guided mikasa to killing him because it would finally shatter ymir the founder's metaphorical shackles and the self-inflicted suffering she's been enduring for 2000 years. liberating ymir would allow the titan powers to disappear from the world, so eldians would have a chance to live normally - in how many generations is irrelevant. with titans and 80% of the world population gone his surviving friends, whom he did love to death (literally) could have full long lives, and paradis itself wasn't at the risk of being attacked anytime soon.
these motivations are neither contradictory nor mutually exclusive. he didn't want mikasa to forget him or fuck other guys because he was in love with her (allegedly) and was a teenager. he didn't want to die and everyone else to move on leaving him behind despite his actions because he's human. he went ahead with wiping out 80% of humanity because he's eren. hange, historia, armin wouldn't have done it, because they're not crazy angsty teens, but eren did. as i said seeing the future and following the visions as well as make a titan munch on his mom just to strengthen his resolve was a stupid plot point that added nothing to the story, but everything makes perfect sense to me.
