He is the younger brother of Hōgen and a leader of 200 soldiers in the Niigata Prefecture.
He looks very similar to his brother but his ears aren't cropped and he has no scars. Though, his front head gets scalped by Akame later in the manga. Also, his eyes are green in the manga (sometimes blue).
Genba was an aggressive and evil dog.
He was less intelligent and more reckless and impulsive than his brother. He also didn't seem to be very independent, working from Hōgen's order and following his brother's ideals and repeating his brother's thoughts instead of his own.
Like his brother, Genba had a perverted liking for females, especially Japanese breeds.
Genba was very sadistic, often wanting to slowly suffocate his opponents and occasionally seeming to enjoy the pain caused to himself. He did not care about his soldiers, and has left them behind to die.
Though described dumb by his brother, he has actually shown more cunning side when he calm and without distractions. Still, he clearly wasn't too smart and was unable to do more complex planning. He admires his brother and seems to be a bit like a puppy in behavior when compared to him.
Ginga Densetsu Weed Manga
Genba was, apparently, born in a lightless shack in a forest close to Northern Alps along with his older brother Hōgen and 18 other dogs. Genba and his brother were rulers of the group thanks to their aggressive nature. The breeder gave them food during their first 6 months of age but suddenly didn't return to feed the dogs (the breeder was a criminal chased by police so it is possible that he went hiding from them). The dogs were left to starve to death.
Hōgen and Genba ate the other dogs to survive. A wild dog called Shingo moved in the area at the time but Genba chased him away by shouting at him.
Six months passed and the owner finally arrived with a dog food bag. 1-year-olds Genba and Hōgen attacked and killed him. Soon afterward, two policemen named Shōji Sudō and Tanuma came to look for the breeder, but instead found the two Great Danes eating his body. When they unlocked the door the two Great Danes fiercely attacked Tanuma. The brothers escaped while Tanuma was killed, and Shōji swore to hunt the brothers down.
Over the next few years, Hōgen and Genba gathered a pack of 400 dogs in the Japanese Alps. They split the pack and Genba moves with his 200 soldiers to Niigata. He works as an ally of his brother and attacks Ōu on his order.
Genba's soldiers face the Kai dogs who try to defend Gajō: Shōji, Buru, Dodo and Shigure. Shigure manages to escape while all the others are killed, Genba himself being the one who killed Shōji. He calls the bodies garbage and throws them off a cliff. Genba makes Gajō his fort and waits for his brother to arrive. He orders his soldiers to steal pet female dogs for him and his brother.
Akame comes to warn Genba that touching the human property will cause trouble but Genba doesn't listen to him. Akame escapes and scalps Genba's front-head as he leaves. When Hōgen finally arrives, Genba greets him happily. Genba is sent to hunt down Akame and other Ōu soldiers with Tōbē but they get in trouble when Weed's pack shows up. Genba is badly wounded in a avalanche caused by Tesshin.
Genba's back legs are completely paralyzed and he gets intellectual disability, unable to recognize even his own brother. He is carried back to the fort by Tōbē. Hōgen is horrified of what happened to his brother. He watches as Genba begins to urinate and drinks it, obviously unaware of what he is really doing, leading to Hōgen mercy-killing him by ripping his brain out. This act seemed cruel to the dogs who were watching, but actually Hōgen fulfilled an old oath he had between his brother: they would die from each other's fangs.
Ginga Densetsu Weed Anime
Genba's role in the anime is somewhat similar but with a few exceptions - the the Great Dane brothers (Hōgen and Genba) only attacked their owner and not the policemen. Genba does encounter Akame, but does not get his head scalped.
Genba also gets wounded in a different way. His legs don't seem to get paralyzed and he becomes very aggressive, while in the manga he seemed to gain intellectual disability instead. Genba's death is off-screen for a second before he is seen being dropped onto the ground by Hōgen.