Gungrave, Gangsta. Recommendations
As the story develops it is similar to Gangsta a bit supernatural, yakuza, friends and their life after being pulled in shady kind of life :)
Both Gungrave and Gangsta are action seinen anime themed around mafia and criminal gangs with lots of violence and gore. Both follows two close friends working together in a city that's corrupt and lawless. Both have a very bleak and dystopian feel to them. Even the character design for two main characters of both of these anime remind of each other.