I don't have an image for it, but, I have to say the death of Fergus McDuck in The Life and Times of Scrooge McDuck.
It's notable for being the only on-panel depiction of a dead duck in the entire Disney Ducks series. Sure, there's been ghosts and tombstones and all those things that implies deaths, but no duck corpses... with one single exception. I read that Don Rosa did not expect Disney to allow that page, let alone that panel at all. But to everyone's surprise, they DID! And thus, the first depiction of a duck, lying dead in his bed at dawn came to be in the story proper, causing many a reader to do a double take.
I'll admit other comics have more powerful deaths, but I'm adding this one to the list simply because there was only one. The father of Scrooge McDuck at the end of chapter 9.