23. John Mongrel
The Numbers Gang is a terrifying South African prison gang, and each section of the gang has a different name and number. John Mongrel, who ranks 23th on our list of worst, most feared, biggest gangsters in the world, joined the gang at the age of 14 when he was imprisoned for murder in 1987, and he became the leader of the 28s, a section of the gang. This gangster claims to have personally killed over 1000 people in jail.
