Candyman
Candyman is a movie that fits a lot of themes into one concise package. A serial killer is terrorizing a low-income area of Chicago, but as it turns out, that serial killer isn't human, or even really interested in killing people. This movie digs more into the idea of systemic poverty as the ultimate crime, so much so that the socio-economic implications feel stronger than the murder itself.
M
That's right, this one is just called M. When a serial killer sets his sights exclusively on hunting children, an unnamed city begins to implode. It takes a village, or in this case, an entire secret gang of criminals, to take this villain to justice. Though you might have never seen it, this film set the precedent for all serial killer movies. That, and this movie still holds up nearly 100 years after its conception