Final answer:
The serial killer with the most proven victims is Luis Garavito from Colombia, with 138 confirmed victims and possibly over 300 total. He primarily targeted young boys and was active from 1992 until his arrest in 1999.
Step-by-step explanation:
The serial killer with the most proven victims worldwide is believed to be Luis Garavito, also known as 'La Bestia' or 'The Beast,' from Colombia. With a confirmed kill count of 138 victims and suspected kills possibly over 300, Garavito targeted young boys between the ages of 6 and 16 over a period of five years from 1992 to 1999. He was eventually captured and convicted in 2000, after his unmistakable pattern and evidence left at crime scenes led to his apprehension. Another prolific serial killer was Harold Shipman from the United Kingdom, a former doctor who was found guilty of murdering 15 of his patients, with estimates of his total victim count ranging up to 250 people.