The Fantastic Four are one of the most interesting teams in the Marvel Universe. Due to the leadership of Mr. Fantastic, the team is frequently focused on science and exploration before being heroes. But that's not what sets them apart from other teams.
They are, first and foremost, a family. Sue and Johnny Storm are siblings. Sue is married to Reed Richards with their kids involved in their adventures. Ben Grimm is so close to them that he's basically family. The problem is when they lose a member, it makes the loss that much harder to bear.
10 Mr. Fantastic and The Invisible Woman Fake Their Deaths
While no one actually died this time, it's almost more tragic because half the Fantastic Four thought the other half did die. After the destruction of the multiverse due to a series of incursions, Reed Richards started to rebuild everything. First, he had to deal with Battleworld's creator, Doctor Doom. He altered Doom's memories so that he wouldn't remember any of what had happened.
The plan was to then take Sue and the Future Foundation off into the new multiverse. Richards decided to leave Human Torch and The Thing behind, altering their memories to think the rest of their family was dead. Well, until Reed needed their help and had to call them. Awkward.
9 Johnny Needs To Clean His Room
Human Torch is generally regarded as the least mature member of the team, which is impressive since there are actual children around the Baxter Building. When his sister, Sue, was on a cleaning rampage one day, he did everything he could to avoid cleaning his room.
This unintentionally led to one of Reed's inventions being activated and releasing a monster that killed Sue. It was a shocking and sudden loss to the entire family. Unable to accept her death, Johnny used Reed's Time Platform to fix the mistake and save his sister.
8 Only Reed Survives
As the incursions became worse and worse, it became clear to the members of the Fantastic Four and the Future Foundation that their universe was doomed. Reed and his son Franklin began working on life rafts to keep as many people as possible alive. When the time came, they all boarded a life raft and tried to survive.
Unfortunately, the raft was damaged, killing all of Reed's family, extended and otherwise. He was the only member left standing. Reed would survive in Battleworld for the next eight years until he found the power to resurrect his family and the multiverse.
7 Human Torch's Sacrifice
Johnny Storm can be immature a significant portion of the time but he's often the first to stand up and do the right thing when the time calls for it. When the Cult of the Negative Zone breached the gate to the Negative Zone, they released a virtually endless swarm of Annihilus Insectoid Soldiers.
Reed and Sue were out of the building, leaving Johnny, Ben and the Future Foundation members there to beat them back. The plan was to push soldiers through the gate, then lock it from the inside. Ben was ready to make the sacrifice when Johnny pushed him to safety and stayed behind. Annihilus killed him when he refused to open the gate.
6 The Thing Returns From Heaven
There's a theory that, all things being equal, The Thing might actually be immortal. Functionally, his rock form doesn't really change or age, meaning he might never die. Well, unless Doctor Doom blasts a hole in his chest or something. That did the trick, killing The Thing and breaking the team apart.
As is so often the case, Reed refused to accept his dear friend's demise. Using a version of Doom's afterlife machine, Reed led the team to the gates of Heaven where they convinced Ben to come back to the land of the living. It's honestly hard to say if they actually did him a favor on that one.
5 Doom Just Can't Let Things Go
You can use a lot of different words to describe Doctor Doom and stubborn is a big one. No matter the situation, it's almost impossible to get the man to change his mind or let something go unless he has a really good reason to. At one point, a monster was attacking his country, Latveria, and he needed help.
He turned to his oldest enemy, Mr. Fantastic, and his team. They helped but the battle left Doom mortally injured. With one last cheap shot, Doom blasted Reed and the two men died together. As sad as this was, it seemed fitting in a strange way that two sides of the same coin would die like that.
4 A Skrull's Choice
Long before the events of Secret Invasion, the Fantastic Four were having problems with Skrulls. One Skrull in particular names Paibok concocted a plan that would see a female Skrull names Lyja replace The Thing's longtime love, Alicia Masters. As time went on, fake Alicia ended up with Johnny Storm and eventually had to reveal herself.
Johnny was less than happy, having to be prevented from killing Lyja. When Paibok's plan came to fruition, Lyja was forced to choose between two parts of her life. Her love for Johnny won out and she died saving him from a blast meant to kill him.
3 Sue Loses A Baby
It's as bad as the title suggests. Pregnant and about to give birth, Reed realized that there were complications he couldn't handle. As such, he turned to Spider-Man's old foe, Doctor Octopus, for help. He's not necessarily the first choice or the best choice but you make do with what you've got. Supposedly, Otto was no longer the villain he once was.
Although he tried, Otto couldn't keep it together long enough to help. Sue would survive but the baby would not, leaving a devastated family behind to mourn the loss. Not all deaths for heroes in the Marvel Universe happen on the battlefield.
2 Doom Stands His Ground
As often as he stands against the Fantastic Four, Doom will stand beside them when the moment calls for it. After the apparent death of the Human Torch in the Negative Zone, Victor von Doom agreed to join the Future Foundation in exchange for Reed helping him regain his lost intelligence.
Doom never does a favor for free. As they searched the multiverse for various Mr. Fantastics, Reed-Alpha kidnapped him and ultimately conscripted him to fight the Mad Celestials. Instead of taking the opportunity to escape, Doom stood his ground and died defending the world.
1 Onslaught Kills Everyone
Born from the powers and collective experiences of Professor X and Magneto, Onslaught quickly became one of the most powerful villains in the history of the Marvel Universe. As the battle against him wore on, it became apparent that a sacrifice needed to be made by the world's non-mutant heroes.
This included the Fantastic Four, who used their bodies to give Onslaught mass the X-Men could attack. When it was all said and done, many of Earth's greatest heroes, and Doctor Doom, appeared to have died. In reality, Franklin Richards created an entire reality for them to survive in. The loss was still devastating at the time.