4. Robert Black
A van driver from the UK, Robert Black discovered that the van driving could access him the opportunity to visit different places on top of accessing the best points for executing his serial killing. He is thought to have specialized in killing small girls and police believe that since 1981 to 1984 he had killed many girls. One of the most brutal serial killers ever, Robert could snatch little from the road or from certain locations where no one was watching. He was finally caught struggling with a six year old girl and got jailed in 1990 for these charges.