An idea

>a rich man intends to commit suicide
>he wants to do this by challenging homeless people to a fight to the death, their prize being all of his wealth
>the homeless eventually unite to protect themselves led by the de facto homeless king
>as this continues the police eventually put together that there is a serial killer targeting the homeless
>in light of this the public are divided, there are those who think the killer is a hero for dealing with the homeless problem, and those who want to see him punished
>charities for the homeless see a spike in donations, with the increased food and kings training they gradually become swole
>some vigilantes also pose as homeless people hoping for the killer to come
>however they end up contesting with copycat killers who believe in the protagonists "cause"
>the police are inching ever closer to our main character
>his battles are becoming much more difficult as he fights vigilantes and homeless now muscled and trained in martial arts
>eventually the situation escalates and reaches the point that the nation is plunged into civil war
>the two factions collide and the war reaches a fever pitch, our protagonists identity as the killer is revealed inadvertently
>now a reluctant leader, he faces his final deathmatch against the homeless king in the wars climax