See Fist of the North Star
In 199X, civilization was ruined as a result of a worldwide nuclear war and many creatures died out. However, mankind survived and entered an age where the strong ruled over the weak, as the few survivors fought over whatever supply of food and uncontaminated water remained in the wasteland of the world. - source Wikipedia
Here, only the strong survive and the weak are sold as slaves or mere worm food.
animes closely similar to this:
Fist of the blue sky by: Tetsuo Hara (with plot supervision by original writer Buronson)
Violence Jack by Go Nagain which is more for the hard core audience and is far more violent and sexual.
This series contains graphic violence, nudity, adult themes and gore , though the gore is edited by making the deaths apear animated as silhouettes and you will see the white gleam of the blood imposed over the black possibly to lower the tone of the nature of the series. Hopefully this will be as general as possible with little to no spoilers.
You follow the journey of the rightful successor of the fictional 2000 year old assassination technique Hokuto no ken, Kenshiro, through a broken post apocalyptic world as the star of death to seal the fist of Raoh and the other stars who have misused their abilities, searches for his beloved Yuria and rights wrongs in a lawless world where people cry out for a savior. The series alludes to Kenshiro as a compassionate messiah figure who imparts justice using his pressure point knowledge and lethal combat habilities that make him god-like. There are others stronger than him and not all the "stars" ( which is a short way to refer to the various schools that use the , Hokuto or Nanto fists which have over 100 sects) are evil.
The constellation based schools are :
Main Hokuto no ken users:
Raoh, Toki, Kenshiro, Jagi
Hokuto Shinken 北斗神拳(divine fist of the north star, loosely on Dim Mak kung fu)
Main Nanto schools and users in the anime:
(南斗聖拳, lit. "Sacred Fist of the South Dipper" and also romanized as Nanto Sei Ken)
Nanto Koshū Ken (南斗孤鷲拳, South Dipper Lone Eagle Fist)
used by Shin
Nanto Suichō Ken (南斗水鳥拳, South Dipper Waterbird Fist, aka Swan Fist or Waterfowl Fist)
used by Rei
Nanto Kōkaku Ken (南斗紅鶴拳, South Dipper Crimson Crane Fist, also translated as the Flamingo Fist)
used by Yuda
Nanto Hakurō Ken (南斗白鷺拳, South Dipper White Heron Fist)
used by: Shū
Nanto Hō-Ō Ken (南斗鳳凰拳, South Dipper Phoenix Fist)
used by: Souther
The Last General of Nanto Roku Seiken (南斗六聖拳最後の将 Nanto Roku Seiken Saigo no Shō?) is a title held by the last surviving member of the Nanto Rokusei blood line. His identity remains unknown until
the last episodes. This general has psychic precognition and is protected by the 5 guardians called the Nanto Goshasei. Each trained in their own unique fighting styles except for the non nonchalant Jūza, who uses a self-taught style and wants nothing to with his mission.
This series features some children side characters that are liked by some or said to be a hindrance.
Be warned, if you dislike them they will continue on the show onto series 2 but they will not take away from the overall experience of this show.
Lin ( a little girl who at times seems connected to Kenshiro and seems to act as an element that humanizes him when he starts to lose his compassion, She is hated by many fans.)
Bat ( a wise cracking, mechanic who is very greedy but ends up helping the group )
Pelu ( a dog added only for the anime, he disappears half way through the series)