Reference

Willem van Eijk earned the nickname "The Beast of Harkstede" (Het Beest van Harkstede) due to the gruesome nature of his crimes and the area where he lived and committed his horrific acts. Van Eijk was convicted of raping and killing several women, with his known victim count being at least five between the 1970s and 2001. His brutality and the sheer terror he caused in the community of Harkstede in the Netherlands led to this ominous moniker.

For more detailed information, you can refer to his Wikipedia page or Murderpedia entry.