Games have been a lot more nuanced nowadays, mostly because storytelling in games has evolved since the days of the NES. Though while many of the brutally dark endings in video game history come from darker, more adult games, sometimes that isn't the case.
Most of the time, cheerful, lighthearted video games have pretty saccharine-sweet endings, with it being a rarity for games with such upbeat tones to have downer endings. But while it is rare for dark endings to appear in cheerful games, there are some notable examples where the developers decided to switch gears towards the end of the game.
The Legend Of Zelda: The Wind Waker (2002/2003)
The Legend of Zelda is no stranger to tonal shifts, but it is The Wind Waker, arguably the best Zelda game, that comes packed with a surprisingly bittersweet ending. Though Wind Waker has some dark and sad moments, they still maintain the game's upbeat tone.
At the end of the game, Link finally manages to kill Ganondorf and save his sister, but this cathartic victory is met with sheer tragedy as King Hyrule sinks to the bottom of the ocean along with what remains of Hyrule, despite Link attempting to save him. King Hyrule's death comes as a true shock as he is a compelling character, but his death also kicks off a new legend.
Sly 2: Band Of Thieves (2004)
Sly 2: Band of Thieves truly created the Sly Cooper formula, establishing the series' stealth gameplay, as well as its James Bond-esque style. That said, its ending takes a severely dark turn when in the final battle with Constable Neyla, who is in control of the body of the villain Clockwork, the mechanical owl's jaws clamp down onto Bentley, critically damaging him.
Cooper then successfully manages to talk Inspector Fox out of arresting Bentley and Murray, with the object of Sly's affection taking him in instead. Though the game ends with Sly escaping in a comedic fashion, the dark ending is so impactful that it carries over into the next game, with Murray still wrestling with his guilt over how slow he was to save Bentley.
Marvel's Spider-Man (2018)
Spider-Man is no stranger to hardships, with the ending of the very upbeat Spider-Man game from Insomniac Games being one that punches the player in the gut. After it's revealed that the person behind the plot to wipe out New York City is Peter's mentor Otto Octavius, he is forced to stop, not just one of his greatest foes, but one of his best friends.
After successfully getting the antidote to the deadly Devil's Breath from Octavius, Spider-Man is able to cure all of those infected save for one person. Aunt May, who was infected, reveals that she knows Peter was Spider-Man and that she's proud of him before allowing herself to die so that he can save the day.
To The Moon (2011)
Sometimes a dark ending isn't an unhappy one, with To The Moon being a prime example of this. To The Moon is an emotional storytelling experience more than a typical game, featuring some really sad cutscenes, an engaging narrative, and an ending that will put a smile on your face, as well as a tear in your eye.
Two scientists use their technology to allow a dying man named Johnny to finally achieve his and his true love River's dream of going to the moon. After the player gets to experience Johnny's memories, they get to see him and River board a rocket and hold hands as the moon enters view, letting Johnny die completely at peace.
Braid (2008/2009)
On the surface, Braid comes across as a cool, if fairly typical platformer, but there is a dark surprise under the game's hood. Throughout the game, the main character Tim goes on an adventure to save a princess that would sound fairly familiar to any fan of the Super Mario series.
The villain who kidnapped the princess is described as a "horrible and evil monster," with that description being pivotal to the endgame. In a shocking Braid twist that was foreshadowed, albeit subtly, it turns out that Tim was the villain all along, with the princess being saved by another hero, leaving Tim all alone.
Undertale's Genocide Ending (2015)
A true love letter to old school RPGs, Undertale is a fun, quirky, enjoyable romp with a hopeful ending, unless the player decides to kill their enemies. One thing that makes Undertale stand out from other RPGs is that the player can choose whether or not the main character Frisk spares or slaughters her foes.
If the player goes on a murder spree, the game shifts to a radically darker tone, with everyone being dead and with the only way for Frisk to redeem herself is to sacrifice her soul. What makes this ending so disturbing is that it's entirely in the player's hand and that if they choose to go down this route, it will affect their subsequent pacifist playthrough.
Klonoa: Door To Phantomile
Klonoa: Door To Phantomile, a precursor to most modern 3D platformers, may seem pretty cutesy on the surface, but don't be fooled. Towards the end of Klonoa and his companion Huepow's adventure, the game's narrative goes in an unexpected and rather dark direction.
After saving the world from the evil Ghadius, Huepow is revealed to be a prince who had brought Klonoa into the world and had implanted memories of his time in Phantomile. The game ends on a sad note as Klonoa is pulled back into his world as Huepow cries, which probably scarred any kids who made it that far.
Conker's Bad Fur Day (2001)
While Conker's Bad Fur Day is a delightfully crass and vulgar game, it's presented in a pseudo-optimistic fashion, albeit with jokes younger players wouldn't get. However, it ends in a surprisingly dark fashion, as when the villainous Panther King reveals that he has been pulling the strings the whole time, he has the duplicitous Don Weezo brutally murder Conker's girlfriend Berri.
When The Panther King is killed by a xenomorph ripoff before immediately being killed by Conker, the alcoholic squirrel is then crowned as king of all the land. However, Conker finds no joy in his newly achieved royalty, as he is surrounded by people he hates and has lost the only person he ever truly loved.