While superhero comics are mostly associated with bright colors and wholesome heroes, that's not always the case. Some comics get dark - really dark - faster than you would expect. Even the most famous and beloved heroes in the world aren't always guaranteed a happy ending. With infinite multiverses and weird versions of each character, there are some stories in which our heroes' fates are as depressing as heck.
It doesn't matter if you're the Man of Steel or the Incredible Hulk - no amount of strength can save you from the existential terrors of your own bad deeds. These are the disturbing future realities where the heroes spend more time wallowing than fighting, and they're honestly hard to accept.
Every story has an end - even the Incredible Hulk's. In this future wasteland, the majority of life on Earth has been wiped out in an atomic conflict. Bruce Banner is one of the few survivors, and he wanders around the wasteland struggling to accept that all the people he loves are gone. An alien robot helps him come to terms with the reality of his situation, warning him that he, too, will want to perish sooner or later.
Eventually, Banner is attacked by a group of giant, radioactive cockroaches. He transforms into the Hulk, but is overwhelmed as the cockroaches eat him alive. He survives the ordeal thanks to his incredible healing, and Banner later watches the video of Hulk being eaten. He comes to the conclusion that he does want to end it all, but Hulk always prevents him from offing himself.
Eventually, the human part of Banner succeeds in perishing, leaving only the Hulk. At first, the green behemoth is relieved to be rid of the puny Banner, but then he says, "Hulk... strongest one there is. Hulk is... only one there is. Only one... there... is. Hulk feels... cold."
Wolverine is a fighter, but even the best fighter can get beaten down by time. In Old Man Logan, Wolverine exists in a future where most heroes are gone and villains rule the Earth. Logan himself has renounced his life as a hero and no longer calls himself Wolverine. When the story begins, he hasn't used his claws in decades and is living a quiet life with his family until they are slain by the Hulk. He's eventually brought back into action by Hawkeye, and we learn how he became so miserable in the first place.
As it turns out, Logan played a critical yet horrifying part in the event that wiped out the heroes. While defending Xavier's academy, he was brainwashed into thinking his fellow mutants were actually enemy combatants. He mercilessly eradicated all his fellow X-Men before realizing his mistake.
The Silver Surfer has often lived in a gray area, acting as a hero or villain depending on the story. The Surfer plays a very different role in the Old Man Quill series, however, as he is effectively turned into a battery.
We learn that the Surfer has been captured by the Universal Church of Truth, who have pledged themselves to aiding the all-consuming Galactus. The Church proceeds to leech the Silver Surfer's cosmic energy and feed it to Galactus, which makes him extremely powerful. The Silver Surfer is trapped in his inert form, unable to do anything other than communicate mentally with Mantis.
In the DC Animated Universe, Tim Drake has a pretty rough time as Robin. In Batman Beyond: Return of the Joker, we see an older Drake who has severed all ties with his Robin alter ego. He also loathes Batman, largely because of an encounter with the Joker that left him mentally scarred.
When Drake was still Batman's young partner, he was taken by the Joker and twisted into "Joker Junior" - a brainwashed minion of the Clown Prince of Crime. After freeing Drake and getting him physical and psychogical help, Batman believed his young ward had been rehabilitated. Unfortunately, the Joker secretly installed a microchip in Drake's brain that restructured Drake on a physical and mental level.
As the new Joker, Drake tries to slay the new Batman, Terry McGinnis. Eventually, McGinnis is able to save him, but the older man is deeply traumatized by the ordeal. It is suggested that he may never get over the side effects of Joker's plot, but he does congratulate the hero on his fine work as the new Batman.