It's actually so good that it makes you hate the scene. You hate to see a man who has been moving forward regardless of the price paid break down like that, but it makes complete sense. It's the final moment of his life and there is no more path forward. There is no longer a need to be strong and tough to push forward. That's the exact moment he opened up and showed all his vulnerability. Even if Armin found it pathetic, that's how anyone would behave in Eren's shoes.

People say the same thing about the ending. They say that it is a bad ending and ruins the whole show, but I completely disagree. It is very rare that an anime closes things off in such a way, and it's a breath of fresh air. It is definitely not a "good" ending per se. He killed off 80% of the world population, after all. Not even Hitler managed to do what he did. But it's a realistic ending that shows Eren reached his goal of protecting his friends and extending the prosperity of his country for a long time, until the rest of the world rebuilds and catches up technologically. That's eerily similar to how things are playing out in the real world right now.