Is it possible to "win" a gang fight?

If you get into a fight with random gang members off the street, the violence will continue to escalate until you do something to reset your gang stars. The more of them you kill, the more "gang stars" you will get, and the more enemies will spawn.

Think of these gang fights like getting in trouble with the police in the GTA series - they will just keep coming, in larger waves and with more force, until you die or you lose your wanted level.

There are some challenges that require you to anger or fight with gang members, and sometimes getting into a random fight is the best way to finish these, but otherwise these fights don't earn you anything beneficial (perhaps aside from small boosts to cash and respect).