Berserk
Berserk is a Grimdark manga written and illustrated by Miura Kentaro. It has seen two anime adaptations of the same name.
The series follows the adventures of the protagonist Guts, who does battle against the forces of darkness with a really, REALLY big sword. In fact, it's probably the only anime/manga in existence where the other characters actually notice that someone's sword is unrealistically large, often pointing out "Fuck me, that's a big swoOH GOD IT CUT ME IN HALF BLARGH". It is, in fact, so large that it cannot actually be used while mounted because swinging it makes the horse fall over. Guts himself can only use it by virtue of training with oversized swords since he was a small child and scaling upwards as he grew, in combination with his titanic (and possibly supernatural) strength.
Chronologically, the story's beginnings are simple gritty medieval violence, following the exploits of a band of mercenaries as they make a name for themselves in the world and acquire power and glory. It swiftly descends into Oh-God-What-the-Fuck-Horror when Eldritch Abominations from Hell and their monstrous "apostles" get in on the action, and via a roundabout series of events Guts ends up hunting down his old companion now ascended to godhood, determined to get revenge for his betrayal.
Just to add to the grimdarkness he has a waifu that got raped by his best friend that turned into a demon. His waifu then had a miscarriage from all the trauma and his kid's fetus comes back to haunt him every day. Later in the series his kid comes back looking about the age of 3-8 years old and saves him and his friends by using terrifyingly effective abilities on par with lofn. Then said kid disappears again leaving a puzzled Guts and a slightly distressed but still insane waifu.
The series has a massive following both in Japan and in the west and has been running for almost two decades. The author, Miura, is well known for taking extended breaks from production, and given his advancing age and his recent statement that he considers the series about one-third complete, has led to fears by many that he will kick the bucket long before he actually finishes the series.
According to some fa/tg/uys Guts is one of the lost Primarchs. Some actually speculate that Guts is Angron's son. Or even Angron himself back in the day or some shit.
/tg/ greatly enjoys it because it's essentially a fucked-up mix of Warhammer 40000, WARMACHINE and D&D 3.5. Furthermore, Guts does display some vestige of humanity, despite all the traumatizing shit that's happened to him he still displays empathy for other people. Where thugs, corrupt guards, and thieves all get chopped to bits in seconds, Guts at least attempts to avoid killing innocents. Insofar as it wont hurt him. For the most part he is an amoral badass/cuntbag, yet there's still a bit of a caring dude in there. Somewhere.
/TG/'s RATING
FIGHTING - 10: Actual varied fighting styles and the main character waving a fuckhuge sword around. Then you've got the monster fights.
GURO - 9001: As one youtuber put it, "GORE!!! GORE!!! BLOOD, TITS GORE!!! GIANT ASS SWORD!!! YOU SEE THAT DEMON? WELL NO YOU DON'T BECAUSE IT'S FUCKING DEAD!!! AGH BLOOD GORE!!! AAAAUUUGHHH!!!" To be more specific you get to see people and creatures get dismembered and mutilated in all kind of fun ways.
Gayness - 9001: As is mandatory for all animu reviewed by /tg/. You've got gay rapists everywhere, and pedophiles abound. Guts was even raped by one as a child, although he killed him later. And then there's Griffith, who, while he isn't gay himself, appears so effeminate it's impossible not to think this.
Moralfaggotry - 0: Gut's lacks any form of moral compass, and it is glorious. Oh, a bunch of innocent little children got turned into monsters through no fault of their own? Don't care, kill 'em all and use their bodily fluids to make myself fireproof. An innocent man being beheaded to get me to come out of hiding? Watch and laugh while he dies. Wound an apostle, fill him full of crossbow bolts... slowly, and then drop a burning building on him and laugh while he burns to death. Well, that's only on the surface. Gutts only asks like an asshole because the last people he cared about all got horrible killed, and most of those things are done out of pure pragmatism. Later he gets some new friends and lightens up place it more of a 5 or 8.
Lulz - 10: So many innocents die in this series, in truly hilarious manners. So do many villains. So do many random background people, as well as inanimate objects and plants. Even main characters aren't safe.
Rape - 9999: Oh God, OH GOD with the rape! If there's one thing that Miura has drilled in our heads for damn sure, it's that nobody is safe from rape in this series. In fact, rape is so prevalent that you can even consider it a theme. Hell, Guts's waifu is such rape bait that three out of five guys are going to try to rape her. Most monsters will try to rape you, most people will try to rape you. In general, most things will try to rape most other things. Even Rape Horse? Especially Rape Horse.
Sickfuckery - 9001: You guys remember the Daemonculaba? Guess what, someone in the Berserk Verse had a similar idea. Take a pregnant woman, dunk her inside the womb of a giant womb-demon, cue demon baby clawing its way out of her stomach. Repeat with entire city population.
MIURA IS ALIIIVEEEE
trolling
The author, having realized it's too boring to continue the story with only Guts, his tinkle fairy and his mental ill waifu, decided to "soften" up the manga a little bit by introducing a loli witch name Schierke and another tinkle fairy from Peter Pan. This causes rage among the fanbase, since they believe Berserk is no longer about a manly, badass mercenary with his vengeance against his homo-looking former comrade, but instead adding side stories about the loli and the shota, even making Schierke naked in front of Guts for some fan service. But since we have seen burning dead children shove each other's asshole with their bee hive and countless of rape and Casca tentacle porn, we can say the author is also a rule 34 fanboy. Besides, it's not like Guts lost his manliness anyway, since he still the only one who gets shit done most of the time.
The manga is shifting its tone from low fantasy grim dark to high fantasy noble bright over time. This is made obvious by the tone shift after Puck reintroduction, Pirkaf shit, Tower of Doom and culminating in him aqcuiring the broken-as-shit Chaos-tainted Power Armor. He slowly open his heart to his new comrades, possibly ending the story in DBZesque 6-volume fighting scene. Basically Miura is moving up from Riddle of Steel, to oWoD, DnD 3.5 and finally finished in Exalted (otherwise he wont stand a chance against the Chaos Gods damn it!)