GTA Killer City is a prime example of a "knock-off" game. It exists solely to capitalize on the keywords "GTA" to trick unsuspecting players into downloading it. It lacks the polish, soul, and technical competence of the games it tries to imitate.
If you are nostalgia for the era of PS2 sandbox crime games but lack a powerful gaming rig, look no further. The offers a fantastic balance of retro aesthetics and modern quality-of-life features. It is violent, it is fast, and it respects your hard drive space.