A Clockwork Orange (1971)

In a dystopian future Britain, Alex DeLarge, a violent youth and leader of a gang, terrorizes the streets with acts of brutality. His reign ends when he’s arrested and convicted of murder. To shorten his sentence, Alex volunteers for an experimental treatment aimed at eradicating his violent tendencies. The program conditions him to detest violence, leaving him defenseless in the same chaotic world he once dominated.