What are the most notable permanent deaths, outside of a characters' origin story? Thus, no examples like Uncle Ben.
Some that come to mind:
Abomination
Baron Heinrich Zemo
Copycat
Genis-Vell
George Stacy
Goliath
Gwen Stacy
Hornet
Jean DeWolff
Justin Hammer
Karen Page
Mar-Vell
Robert Kelly
Thunderbird
Of course, comics being what they are, who knows if this ends up getting contradicted later. Anyways, what other notable examples are there?