Logic dictates that a dark and overbearing anime would be populated by characters who share their world's pessimistic outlook. That isn't the case for these characters, who not only managed to find the bright side of life but actively enjoy their hellish environments.
Some found a way to remain blissfully ignorant of their respective world's foreboding sense of doom, while others actually want to see how their worlds end just for fun's sake. Either way, nothing - not even death itself - can dampen these people's spirits.
WARNING: Spoilers ahead.
10 Black Lagoon - Leigharch Was Too High To Care About Roanapur's Darkness
Everyone who works or lives in Roanapur is prone to letting their bloodlust (or what Dutch calls Whitman Fever) take hold, but these instances are fleeting. Such moments are only the symptoms of Black Lagoon's endemic nihilism that forces the mercenaries to hide behind badass posturing, which is what makes Leigharch stand out.
In brief, Leigharch is either too high on cocaine (manga) or marijuana (anime) to care about guilt or morality. This only made his driving better, though he'd credit that to Capt. Picard and the Playboy Bunnies he sees in his constant hallucinations. Unfortunately, Shenhua claims he overdosed and has yet to return from Mars.
9 Jujutsu Kaisen - Aoi Todo Is An Idol Fan Who Just Wanted To Find A Bro
A core theme of Jujutsu Kaisen is the willingness to accept death; sorcerers and curses alike know that they can die at any moment, so they try to put on a brave face no matter what. Meanwhile, Todo doesn't care much about the fragility of his mortal existence because his favorite idol Takada-chan has an upcoming show.
Unlike his fellow sorcerers, Todo doesn't take his obligations seriously. As far as he's concerned, it's just a means to his end of finding a kindred soul to call his "Bro." That, and he finds beating up enemies to be immensely fun. Fortunately for Todo, he found what he was looking for in Yuji Itadori, though the latter would beg to differ.
8 Rebuild Of Evangelion - Mari Illustrious Makinami Loves Getting In Her Robot
Neon Genesis Evangelion is known for its emotionally tortured pilots who struggle to stay sane in a dying world, but the Rebuild movies threw a wrench in this tradition. First appearing in Evangelion 2.0: You Can (Not) Advance, Mari is by far the only Eva pilot who wholeheartedly loves her job of piloting the disturbing Freudian mechs.
While she may have ulterior motives for fighting alongside NERV (or WILLE later on), Mari has no known baggage and legitimately enjoys piloting her Eva. Her true motivations and backstory may finally be revealed in Evangelion 3.0 + 1.0 Thrice Upon A Time, though no one's expecting her jarringly bubbly demeanor to change.
7 Attack On Titan - Hange Zoe Is The Only Soldier Who Thinks Titans Are Cool
The world of Attack on Titan is one of the darkest seen in recent anime memory, especially when its characters' only long-term life choices are living in a glorified prison or getting devoured by a giant cannibal. But while everyone understandably fears or hates the Titans, Hange Zoe is fascinated by them.
The Titans' mysterious origins and the Shifters' seemingly countless forms excite Hange, so much so that their fellow soldiers find Hange creepier than a Titan's smile. That said, Hange's eccentricity is an alternative to their original furious bloodlust, which often resurfaced in moments of dire stakes and stress.
6 Tokyo Ghoul - Shuu Tsukiyama Reveled In Flamboyant Cannibalism
Life in Tokyo Ghoul is not easy for both humans and Ghouls. The humans live in mortal fear of being devoured by a Ghoul, while Ghouls yearn for a place in society where they're not hunted down. One of the few who found luxury in this world's darkness was Shuu, better known as the Gourmet Ghoul.
Despite being known for eating people only after torturing them, Shuu believed himself to be high class. His main goal is to experience the best tastes life has to offer, whether it's in human flesh or the art that he hoards. He developed an obsession for Kaneki, and he won't let anything get in the way of his one-sided affection.
5 Danganronpa The Animation - Junko Enoshima Found Joy In Despair
Since it's the definitive death game anime, Danganronpa is unsurprisingly dark and harrowing. Here, students are trapped in Hope Peak Academy, where they must commit the perfect murder and get away with it to graduate. Overseeing everything is Monokuma, a sadistic teddy bear and headmaster. Monokuma is only the mastermind's front, though, and it's revealed that Junko orchestrated everything from the beginning.
Junko can only feel pleasure when inflicting pain, which she did through Monokuma's sanity-breaking speeches and throwing deadly curveballs whenever she got bored. In fact, Junko enjoyed sowing discord so much that she looked forward to her execution. But even before fessing up, Junko was the excitable fashionista everyone wanted to befriend.
4 Beastars - Riz Could Barely Hide His Murderous Instincts
Beastars' anthropomorphic world can be disarmingly welcoming, since its inter-species society is wrought with deep prejudices and unspoken castes. Cherryton Academy is one of the few safe spaces in this unforgiving world, and it's the scene of a vicious murder that rocked the student body.
Riz, the friendly grizzly bear from the theater club, is the culprit, but his overly friendly persona did a good job of covering up his murderous side. Legoshi and Pina saw through Riz's façade, and to say Riz lost his cool is an understatement. By Season 2's end, Riz embraced his bloodlust and nearly ate his schoolmates in a fit of rage.
3 Death Note - Ryuk Enjoyed The Show Of A Lifetime
Unlike Light Yagami, Ryuk had no grand designs or delusions; he dropped his Death Note on Earth because he was bored. Luckily for Ryuk, a certain teenage prodigy with a god complex picked it up and tried to reshape the world in his image, thus giving the Shinigami the best entertainment he's had in eons.
From Death Note's start to end, Ryuk hung out with Light just to see what crazy things would he'd do next as Kira. While Light took his self-anointed godhood seriously, Ryuk watched with glee. When Ryuk wasn't egging Kira on, he was either munching on apples or being fascinated by the most mundane parts of mortal life.
2 Hellsing Ultimate - Hellsing, Iscariot, & Millennium Had A Blast In London
Despite living in a world where vampires and vampire Nazis are a constant threat, almost everyone in Hellsing Ultimate seemed to be having fun. Even more reserved people like Seras Victoria eventually gave in to the joys of the slaughter, joining Alucard and The Major in their love of carnage.
This bloodthirsty joy hit its zenith during the Battle of London, when all sides of the conflict converged on the British capital. As Millennium waged the war it always wanted, the Hellsing Organization and Iscariot relished in the once-in-a-generation chance to flex their respective murderous might in public.
1 Dorohedoro - Death & Torture Is Just Everyday Life For Everyone
Dorohedoro's world is split into two distinct regions, with Magic Users enjoying themselves in a high class dimension as the humans stick to the slums known as The Hole. Magic Users callously abduct random people to test their spells on, while humans brutally kill any Magic User who winds up in The Hole.
Despite all that, everyone in the anime is rather chipper. Kaiman and his best friend Nikaido cheerily kill Magic Users before lunchtime, while En and his found family of Magic Users genuinely watch out for each other. Death and fates worse than it are so normalized in this world that nobody can be really bothered to dread or mourn it.