A sociopath is a person with a mental illness that manifests in extremely antisocial behavior and the inability to distinguish right from wrong. You're probably right to be afraid of a sociopath.
Pathology means illness, and so socio- pathology means social illness. If someone is a sociopath, that means that they have a social sickness––they lack the ability to be social. Many movies and TV crime shows feature plots involving sociopaths, but hopefully the TV is the only place you ever encounter sociopaths.