Sometimes they live forever, and sometimes they drop like flies. And then there are those heroes whose deaths are pivotal to a storyline and change it forever. Here are a few of those deaths that had substance and weren't necessarily for shock value alone.
Bill Foster (Giant-Man)
Call this the shot heard round the Civil War. Marvel had slowly ratcheted up the tension with each issue of Civil War, but this was the one that changed the tide in the storyline. The sudden reappearance of Thor made everyone giddy as we saw Cap's rebels facing their hardest foe ever. Giant Man rushed in to give Thor "the shortest comeback ever", when suddenly Thor killed him! That one unexpected moment was a jaw-dropper everywhere. It's not that Foster was that great of a character (though he had been around for over a decade), it was the fact that a hero actually died--and he was killed by Thor no less!
Later we learned that it wasn't Thor but was actually a clone created by Reed Richards, but that didn't stop the death from being real to us. It changed the entire landscape of the Civil War, and even managed to force many heroes to change sides (on both sides) when they saw what had happened. Rebels became Registered, and vice-versa. It was well-done and not gimmicky in any way. The transition to Bill's nephew (seeking revenge for his uncle's death) of the "Giant-Man" mantle made sense.
Ant-Man (Scott Lang)
The replacement Ant-Man had a long and illustrious career as a hero wearing Hank Pym's original suit. Scott Lang even managed to be a part of the Fantastic Four for a while when Reed Richards was believed dead. It wasn't until he was finally a full-time member of the Avengers that his number was up.
The Avengers Disassembled storyline began with Scott's death at the hands of the resurrected Jack-of-Hearts. With that death, Marvel had made it clear that this was not just some simple multi-part storyline that would fade into oblivion quietly in a few months.
Call it what you will, that particular story gave us more collateral damage in 4 issues than we'd seen in the years before it. Hawkeye also died two issues later (though he soon returned), and She-Hulk went bonkers and killed the Vision. Marvel was doing all it could to show us they were planning to change the face of the Avengers forever.
Did the change last? No. It was less than three months later before we saw the first issue of The New Avengers, followed soon after that by The Mighty Avengers (and now we're about to see The Dark Avengers coming up). Still, Scott's death was the first and still holds. He could never be considered a major player in the Marvel Universe, but his death set the stage for the destruction of the Avengers for a short while.
Kraven the Hunter
Why would the death of one of Spider-Man's oldest foes find its way onto the list? Simple: Kraven did what no other villain had ever succeeded in doing before. Captured on a rooftop one rainy night, Spider-Man prepared for some long speech and a brilliant escape. Instead, Kraven pulled out a rifle and shot him! Even though he didn't actually kill Spider-Man (but we sure thought he did for an issue or two), he actually proved himself Spider-Man's superior and even took his place. Through the years of Doc Ock, Vulture, Shocker, Electro, and dozens of others, Kraven alone "killed" the Spider.
After showing himself Spider-Man's better, we thought the story was over. The truth was that Marvel was saving one last major plot twist that came out of nowhere and changed the landscape of Spider-Man's rogue's gallery forever. Kraven pulled out a shotgun and proceeded to ventilate his head, giving us the first death of any major Spider-Man villain to date--and from suicide, no less. This truly was Kraven's Last Hunt.
While the Spider-Man storyline The Other managed to top this by actually giving us the death of Peter Parker (and of course, his return), Marvel lived up to the hype with this one for a little while. Unfortunately we've had to deal with a number of Kraven's relatives who have come through the ranks to take his place, but the original--and still the best--is no longer with us, giving mortality to those iconic Spider-villains we sometimes take for granted.
Janet Van Dyne (The Wasp)
The Skrull's Secret Invasion was one of the strongest things Marvel has put out in a while. It followed the heels of Civil War with a story that ratcheted up the tension even further than before as we were suddenly made aware of the fact that many of the heroes we thought we knew were in actuality something far more sinister.
Through defeat after defeat, Marvel's heroes bravely fought back against a far superior and better-prepared enemy. Then with the return of Reed Richards the tide turned and we saw the heroes start to get the upper hand. It was at that time that the Skrulls unleashed their secret weapon: Janet Van Dyne.
Given a new growth formula by the Hank Pym Skrull in the first issue of Mighty Avengers, the significance of that gift suddenly became apparent as Janet went nuclear in the midst of the heroes. Only the intervention of the newly-returned Thor kept the body count down to one in the middle of the chaos.
It was a parting shot in the final issue of the story, and it served to motivate the heroes to annihilate the remainder of the Skrull army. It also served to set Hank Pym against Tony Stark in the following issue of Mighty Avengers, and who knows where that might lead. Of course, we know she's coming back some day, but for now her death has caused major ripples in the Marvel U.
Jack Munroe (Nomad)
First he was the sidekick, then he became a hero in his own right, then he became a villain called Scourge, before finally settling in to die from the Super-Soldier Serum that had made him a hero in the first place. But a slow death was not what fate (and Marvel) had in store for Jack Munroe.
The appearance of the Winter Soldier in the new Captain America series had some folks wondering. He looked a whole lot like Jack Munroe, and there were many rumors flying around that he might just be Cap's new villain.
It was Jack's death at the hands of the Winter Soldier that managed to settle that argument once and for all. Marvel made it plain and certain that Jack really was dead too, giving us a few parting panels of Jack's glassy-eyed stare as he was unceremoniously crammed into the trunk of a car.
The storyline later tried to take a turn by having Cap even think it might be Jack for a little while before the truth came out that Bucky Barnes had found his way back from the grave. Still, Jack's death was important because he was the first sidekick to be taken down by another sidekick, and it was the first real death by someone close to Cap in this new storyline that would eventually lead to Bucky taking Cap's place after his own death.
Before heroes started killing heroes in Civil War, we had Wolverine taking them out in "Enemy of the State". Brainwashed by Hydra, Wolverine tore into SHIELD and a bunch of the good guys before finally getting his mind back and taking the fight to his tormentors. One of the casualties during his brainwashed phase was former Alpha Flight hero turned X-Men hero Northstar.
Northstar could in no way be considered anything more than a C-list character, but his death makes the list simply because Wolverine took him down...and it wasn't even a "What If?" story or anything! Of course, he only stayed dead a few issues before coming back as a Hand agent (brought back from the dead). And of course, it begs the question that if he's supposed to be a super-speedster, how on Earth did he get pinned to the tree by Wolverine instead of flying away? Not as fast as he thought, I guess.