Eren has to win. The world became a villain, and Eren fought back.
There is nothing wrong with that. Will there be sad stories, and innocents who die? Yes, that's war.
But WHO started this war? The 'civilized' countries of the world! For greed! FOR WEALTH! They would massacre Paradis just to line their fucking pockets! They even decided it at a fancy dress event, with wine!
Eren's only 'bad' because he's STRONGER THAN THEY ARE! They fucked with someone stronger than them, so now they're the ones being massacred instead of the innocent Paradisians! As much as I like Hange, she and her 'Eren Resistance' are blood traitors! They're trying to save the people who wanted to kill them, visit untold suffering on the survivors, and rape the land of its wealth after shoveling Paradisian corpses out of the way! And if they manage it, the world will choose to KILL THEM for fear of another Founder Titan appearing! The world will murder its saviors for their own imagined continued safety and prosperity!
This isn't the story of evil mean Eren going too far, it's the oppressed people deciding they will not go easily into death just because their masters say so! Rise up, Founding Titan! Shoulder the burden of destroying the enemies, even if the survivors of your people hate you forever, because at least they'll be alive and thriving enough to do so!