Grand Theft Auto III - The Definitive Edition
44 Achievements
PC
Street Sweeper
Waste 100 gang members.
How to unlock the Street Sweeper achievement in Grand Theft Auto III - The Definitive Edition - Definitive Guide
This will easily come naturally especially if you are completing the rampages. If you want it sooner then head into a gang area (e.g. Chinatown for the triads) and just start killing them until it unlocks.