Violence Jack is a manga by Go Nagai that was released from 1973 to 1990. It's a sequel to Devilman and both a sequel and prequel to Devilman Lady. The series is particularly infamous for not only including large amounts of sex and gory violence, but also has cameos from several of Go Nagai's other manga as well. In fact, many of the chapters seem to be dedicated to taking classic Go Nagai series and then Deconstructing them by placing them in Violence Jack's brutal setting.The entire Kanto region of Japan is destroyed in both an earthquake and a volcanic eruption. Any survivors are now forced to fight for their lives, due to biker gangs and warlords having taken over. The worst of them is the Slum King, who practically has all of Kanto under his control.Luckily, there's Violence Jack, a mysterious, gigantic man with an equally gigantic knife. Unluckily, he's not exactly careful about collateral damage or danger to bystanders, although he's still the closest approximation to a good guy in this Crapsack World. Jack travels around Kanto, killing warlords and, eventually, the Slum King himself.Violence Jack has three OAVs based on three different arcs from the manga (Harlem Bomber, Evil Town, and Hell's Wind). All three have been released in the US, the UK, Italy, and France, but were heavily censored (especially Evil Town). It wasn't until a few years later that uncensored editions were released.The series got a short revival in 2005, a short 2 Volume adventure under the title of Shin Violence Jack.As for the manga, the only place it's ever been released outside of Japan is Italy and very few arcs have been scanlated into English.
Amnesiac Hero: Having no idea who he is (and generally not caring), the titular character named himself after his violent fame — Violence — and iconic knife — Jack. Being Akira Fudoh, he has no recollection of the events that occurred in Devilman.
Armies Are Evil: Generally, the biggest villains will have their own armies, starting with the Slum King himself. Subverted in the case of good guys like orphan boy Ryou Takuma and others who lead armies against the Slum King.
Special mention goes to the Marvel Pirates in Shin Violence Jack, who are all former U.S. Marines. They use their training to murder, rape and pillage throughout Tokyo Bay.
Back from the Dead: Violence Jack is Akira Fudoh reincarnated as the Human Avatar of Death.
The Slum Queen and Miki Makimura appear at the end of volume 1 of Shin Violence Jack. The former refers to herself as "Queen", while the latter has the body of a dog.
Though dog-Miki is actually revealed to be her face, with the rest of her body locked up in the Skull King's dungeon at the Skull Castle. At the end of Shin Violence Jack she gets her face back and becomes some sort of warrior woman with Cerberus as her steed.
The Yakuza Heretic leader whom Jack beheaded at the Earthquake Fortress in volume two of the original Violence Jack manga returns as a demon who challenges Jack to a rematch. Before Jack can respond, the Heretic leader is attacked by the townspeople and burned to death.
Bondage Is Bad: Many villains (in the Harlem Bomber OAV) are S&M costume-wearing weirdos who like to tie up and sexually torture innocent young women.
Character Development: Jack during his streaks of violent rampage in the post-apocalyptic world. Initially he made it clear that he didn't care whom he was fighting or saving — it was all collateral whether he felt like saving/killing one person here or there. However as the series progressed, Jack became quite focused on saving people, mostly women and children. After his new-found resolve, the body count of people who sought his help dropped considerably.
Cloudcuckoolander: The New Shu Army in Shin Violence Jack. They are a group of Chinese and Japanese actors and extras who were filming a movie based on the Romance of the Three Kingdoms. When the Kanto Hellquake struck, they went collectively insane and began to think that they were real heroes from China's Three Kingdoms era. Their three leaders seek to take Kanto, a "land stripped of history and culture," and turn it into a tyrannical state for the strong, using the ancient China motif to keep their men unified. In that respect they resemble Caesar from Fallout New Vegas. Oh, and they are also Ax Crazy killers who terrorize the populace.
Cosmic Retcon: Devilman Lady ended with one of these, erasing all of what happened since Mao Dante up to the original Violence Jack; Shin Violence Jack is the new begining of the entire related Nagai universe.
And Devilman Grimoire may very well be the sequel to Shin Violence Jack in this new related Nagai universe.
Crapsack World: Even worse than the world of the series to which it's a sequel.
Genius Bruiser: Apart from being an excellent hand-to-hand combatant with great mystical powers, Jack is also shown to know ancient Chinese history in Shin Violence Jack.
Gorn: The entire series. A prominent example is in Evil Town when Evil Redhead Bitch kills all the children and when Mad Saurus eats the corpse of his gay lover to "gain his power".
Fate Worse Than Death: Ryo Asuka and Miki Makimura are brought back to life to be the Slum King's sex slaves. It turns out Ryo/Satan wanted this as his punishment for killing Devilman.
Friend to All Children: In the original manga Jack was often saving children in the post-apocalyptic world, mostly unintentional or just because he felt like it; In the series revival in 2005, it seems that children have grown on Jack's heart, he is even a self-proclaimed defender of children.
Hijacked by Ganon: Slum King is the supreme warlord of the post-apocalyptic world with no equal, it was by Satan's own will that Slum King reigned; except that when Slum King's slave, Ryo Asuka, sacrificed himself to help Jack kill the warlord, Satan came back and quickly killed the Slum King, wanting to resume the eternal grudge between Violence Jack (Akira Fudou) and Ryo Asuka (Satan) in yet another epic fight.
Major Injury Underreaction: Jack is king of this trope. In the third OAV, the Hell's Wind gang shoots him with automatic weapons for nearly a good five minutes. He turns to yell something about taking a picture at the kid watching.
No Ending: Shin Violence Jack climaxes with the Skull King possibly remembering he's the Slum King, and gets a never-seen-before face strikingly similar to Akira's to boot, Miki gets her body back and apparently has psychic powers now... and that's how it ends.
Although Skull King's true identity may actually be Akira Fudo, with Violence Jack implied to be Amon.
Rape as Backstory: In the Evil Town arc, the reason Aila Mu and the other women of Area C refuse to associate themselves with Area A is because the men of Area A raped them shortly after the earthquake.
Shingo in the "King of Brutes", due to looking like a girl all his life.
Sequel Reset: The original manga ended with Jack fighting against Satan, but with no clear conclusion on the fight's outcome, Shin Violence Jack comes and Jack is back to killing warlords and other opressors from Slum King's remains, at least his Character Development sticks for this one.
Unbuilt Trope: "Violence Jack" was probably the first After the End manga published in Japan. Compared to it, manga set in a post-apocalyptic setting, such as Fist of the North Star, are Lighter and Softer. The manga devotes its entire first chapter to showing how it all happened — with plentiful Nightmare Fuel scenes of people dying awfully, lovingly depicted by Go Nagai — including a very tense build-up to the earthquake — providing plentiful geographical details and giving a death toll. And afterwards it shows that the resulting world is a Crapsack World where people suffer horrific death and abuse at the hands of the worst villains Go Nagai has put to paper, things ALWAYS go From Bad to Worse, and The Hero is rather a Villain Protagonist who does not feel compelled to protect helpless people and only intervenes into a fight if something draws his attention or he would like bust some heads.
Vasquez Always Dies: In the Evil Town story, muscle girl Ricki gets torn to pieces, while most of the more feminine women live on.