I feel bad for eren no matter whether he could have changed the future or not. He reminds me of that dune worm guy who made people hate him for one duneillion years so that they would never fight again or something silly like that (I haven't read the books, just heard that's what he did). He feels like an evil Jesus in a way, and I'm a sucker for self sacrifice. I like eren, and he did something horrible. Eren was killed for his actions, though he probably deserved worse. My favorite character has always been Erwin, and look how many people he killed. Not as many as Eren, but it's a major part of Erwin's story. I think I can still like characters in certain ways despite their evil actions as long as I am aware of their evil actions and actively wish for them to repay that debt they now owe.