Bucky
Bucky Barnes was Captain America's partner in World War II, fighting Nazis with his plucky youthful optimism and strong right cross. Sadly, Bucky was killed near the end of WWII, trying to defuse Baron Zemo's buzz bomb from hitting London.
Bucky's death was one of the few deaths in comics that you could count on sticking. Even as others died and came back, Bucky stayed a consistent and reassuring dead. You knew that he was hanging out peacefully in Heaven, making friends with Uncle Ben, Barry Allen and Bob Hope.
But sadly, this is comics, and no one ever stays dead. Writer Ed Brubaker resurrected Bucky survived as the brainwashed Russian assassin known as the Winter Soldier, which turned out to be a pretty good story. So I don't mind that Bucky's back - but Uncle Ben better stay dead, dammit.