As an absolute 'Attack on Titan' geek, it's still painful to recall Commander Erwin Smith's departure! Sadly, it happens quite late in the series; in the anime adaptation's third season, specifically in episode 18 titled "Hero".
Erwin's charge towards the Beast Titan, waving a torch with his remaining soldiers, is still etched in my mind. It's devastating, but also beautiful in the sense of the sacrifice he made, demonstrating his leadership and passion for humanity. He may have fallen, but his spirit lives on, motivating everyone to fight for freedom.