Darker and Edgier/Fan Works

See also Dark Fic.

Dragon Ball Abridged's Freeza manages to surpass the original's already incredible level of monstrousness. Examples include him not caring whatsoever happens to his minions, deciding what wine to have for dinner before killing someone, and singing a variation of My Favorite Things before he impales Krillin.
New World. The very first chapter features a Scyther beheading another Pokemon and then then being horrifically and disgustingly killed. It is implied that the story takes place a long time after an apocalyptic event. Pokemon are perfectly willing and able to kill humans and other Pokemon.
Warhammer 40000 Trouble. War Fic, in our Harem Comedy story? Yes. It Makes Sense in Context? HELL YES! Everyone Took a Level in Badass? FUCK YEAH, especially everyone that already Badass in the original story but Played for Drama instead. That's before we add Warhammer 40,000 into account...
Let's not forget My Immortal, in which most of the characters have converted to ~~Satanism~~ "STANISM", Harry's scar is now a pentegram, and all the characters seem to do is Wangst around, cut their wrists, go to My Chemical Romance concerts, have sex, and proclaim how ~~gothic~~ "goffik" they are. The irony being that, for all its posturing, it's not nearly as dark as the actual later books of the series, for which see Literature below.
Pokémon has gotten a makeover with the advent of The Sun Soul, which combines a pointed Deconstruction with an Anyone Can Die attitude. So far, if the reviews and forum opinions are to be believed, the fandom approves.
Challenge of the Super Friends: The End, where the Legion of Doom travel to a horrific Lovecraftian universe and end up like victims in the Event Horizon and Hellraiser films, while the Superfriends become fascistic and attempt to make their world a utopia in the villains' absence.
This fanfic is a considerably Darker And Edgier version of the more light-hearted, facetious Doom Repercussions of Evil.
This Photoshop Phriday depicts Children's Books as "serious" Hollywood movies
Aeon Natum Engel takes Neon Genesis Evangelion and makes it darker by removing most of the elements that made the original dark, giving everyone mandatory psychological counseling, making the characters competent... and introducing the Cthulhu Mythos.
Angel Island Zone. A retelling of the events of Sonic 3 from Knuckles' end of things. More blood, more tears, more drama, and more character development. And surprisingly, it manages to pull it off quite well.
Soulless shell attempted this.
The Road This Far Can't Be Retraced, a Scooby Doo fanfic, and the t-shirt design it was inspired by.
- You're Ready and You're Willin' by Hector Rashburn is in the same vein. Yes, there are two fanfics based on a t-shirt. Never underestimate the power of fandom.
Tiberium Wars manages to make the Command & Conquer Tiberium universe even darker than it already is, by virtue of introducing War Is Hell to show just how horrific the battles and weaponry in the setting really are.
Latias' Journey is an awesome, hilarious but hellish Pokémon fan fic.
Twilight Valley, Out of the Shadows are both very dark Land Before Time fan fictions.
Take Axis Powers Hetalia- a cute, comedic series about anthropomorphised countries- twist history a bit, add a good dosage of mind screwing and a bizarre love quadrangle, and you get All He Ever Wanted, a series of fanfics set in a world where England is on the Axis Powers' side, America is Communist, Prussia is a batshit Nazi and rape machine, Austria is suddenly Jewish, Hungary and Liechtenstein are raped, and everyone's suffering for it. The fandom's opinion on it... well, it's very mixed.
- Note that the AHEW crew are not the first nor the last to give this particular series this makeover. The Hetalia fandom as a whole is greatly enamored with the trope. The results... well, are varied.
Here are three little vignettes, fan fiction of Super Mario Bros...in the style of Frank Miller!
The Oneiroi Series is notorious with fans for this. While Order of the Stick is not Light And Fluffy, the series is darker with frequent (VERY frequent) sex-related violence (usually rape) and a potential Downer Ending, as well as the fact it has very dark themes involving the relationship between children and their parents (or parental substitutes) and generally the role of adults and family in raising a kid. It's very specific.
Falling Stars takes the characters of Lucky Star and places them into the Capital Wasteland. Needless to say, it's not nearly as cheery as the original source material.
Ann-Kathrin Kniggendorf and Trivia make an art form of this in Galaxy Rangers fandom.
For Every Action an Atomic Betty fanfic that practically runs on this trope.
Twisted Disney Princesses.
Powerpuff Girls Doujinshi and its spin-off Grim Tales from Down Below are both examples of this trope done extraordinarily well, provided you can get past all the fluffy kids' cartoons going through this process in the first place.
The constant and unrelenting use of this trope in Pokémon fanfic spawned this parody, which also doubles as a parody of grimdark movie reboots in general.
The Urthblood Saga is in most ways darker and more mature than the official Redwall novels; the wars and violence are more graphic and disturbing, the heroes are often of rather questionable morality and are much less protected by the Plot Armor, it's generally more on the cynical side, and the good guys (depending on who you view as the "good guys") do not always win. It still has plenty of light, humorous and heartwarming moments though, and it's actually far more idealistic than the official series in regards to the vermin being able to turn good, which is one of its central themes.
The Pokémon anime has taken on a darker edge with Cornova's Poke Wars. It is much more violent, cynical, grittier and much less idealistic than the anime it was based on.
The Tamers Forever Series, to the point where it's been favourably compared to Evangelion.
- A great example of Tropes Are Not Bad.
For a show as innocuous as My Little Pony Friendship Is Magic, there is quite a substantial amount of fan media with this in mind. One of the most notable examples is Cupcakes, a fan fiction that has gained memetic status within the Brony community for its rather horrifying portrayal of Pinkie Pie and her cupcake recipe. Another example would be Fallout Equestria, a MLP and Fallout crossover featuring a post-apocalyptic Equestria.
The Terrible Secret of Animal Crossing, a fanfic mixed with Let's Play, does this to Animal Crossing.
Winter War takes the darkest elements of Bleach and runs with them. Bleach can get pretty violent, but it's usually contained in one-on-one duels, the only people who die are villains, and no matter how badly a good guy is hurt, they're unlikely to suffer any lasting consequences to it. Winter War throws that all out the window. Heroes die. Heroes will fight dishonorably or gang up on opponents if they have to. There are limits to what healers can do, and lingering injuries complicate daily life and battle alike. Aizen's Hollowfication experiments are shown as horrific and dehumanizing rather than being used as a source of power-ups. And the authors don't pull punches about the likely states of mind of people who've been on the front lines- or taken captive, or waiting back home for loved ones who are probably dead- for months.
Team Fortress 2 is normally quite a violent game, but always in a light-hearted and comedic way. Respawn of the Dead, on the other hand, is brutal and disturbing in its violence and very, very dark. Cat Bountry takes the personal quirks of the characters and expands them into full-blown psychosis. The result is actually quite good.
- Cuanta Vida has moments of this as well, although in a very different way, largely by actually confronting some of the inherent Fridge Horror of the premise of the games. The fact that the characters are actually somewhat toned down from their portrayal in-game somehow only makes it worse.
Koishi Komeijis Heart Throbbing Adventure tells the story of Komeiji Koishi. It starts out innocent enough, but by Episode 8 we have Koishi getting all of her limbs cut off and left to die on the floor. Until she gets decapitated.
- And then she starts attaching the limbs and head of Yukari's corpse to her body.
Alexandra Quick is this to Harry Potter, although in a way that doesn't go to the extremes of Darkfic or seem out of place with the mood of the original series. People do start dying in the first book though and there are some dark, dark plots in Wizarding America. Things get that way when you have wizards as government and wizards as terrorist with Black and Grey Morality and you don't know which is which.
Quite a few in the Kirby fanfic Nightmarefics, with chapter 14 being the most notable example.
Look up The Amazing World of Gumball on Fanfiction.net. Get ready to see a lot of Dark Fics.
Sherlock Holmes AU fic A Study in Regret is this, having killed off Watson before the first chapter and opening with Holmes undergoing Cold-Blooded Torture while Locked in the Dungeon.
Another Sherlockian example is Mortality in the Deliver Us from Evil Series, with more Holmes!torture, Nightmare Fuel, and general angst.
Yet another Sherlockian example: The Ghost Map. Epidemic, character death, enforced suicide, not to mention a Bigger Bad that's Not Quite Dead... yeeeah, I'd say we have a Darker and Edgier Alternate Universe, here.