From the Giggling Granny to the Candy Man, history’s worst serial killers are somehow even more disturbing than they sound.

The worst serial killers in history are more terrifying than any horror movie. No make-believe monster will ever match the ferocity of murderers like Ed Kemper, who murdered and mutilated eight women, including his own mother, or Belle Gunness, who lured dozens of hopeful bachelors to her Indiana farm and fed them to her pigs.

So who is history’s worst serial killer? It depends. There are certainly candidates like Luis Garavito. The so-called “Beast” of Columbia, Garavito murdered between 100 to 400 boys, all between the ages of six and 16, and may be the most prolific serial killer in human history.

Then again, there are also serial killers like Gary Ridgway. Between 1982 to 1998, he targeted vulnerable women in Washington State as the so-called “Green River Killer,” killing as many as 70 people before he was finally caught. By many estimates, Ridgeway is the worst serial killer in U.S. history, though his record may be surpassed by killers like Samuel Little.

Still, though Ridgway may be the deadliest serial killer in American history, many believe that the “worst serial killer” title surely belongs to Ted Bundy. Bundy didn’t have Ridgway’s kill count — he killed at least 30 women between 1974 and 1978 — but his bloodthirsty ferocity toward his victims has made him one of the most infamous killers of all.

Luis Garavito, The ‘Beast’ Of Colombia

In 1997, a mass grave was discovered in Pereira, Colombia, with 25 bodies in such a state that police suspected that a Satanic cult was behind it. In fact, it was the work of a single man: Luis Garavito, and made up just a small proportion of his hundreds of alleged victims.

Public DomainLuis Garavito, who may have killed as many as 400 children, is considered by many as the worst serial killer in human history.

Born in 1957, Garavito and his brothers were allegedly abused by their father. And as an adult, Garavito started abusing young boys himself. He targeted homeless and orphaned young boys, many of whom ended up on the streets because of a decades-long civil war that tore through Colombia.

Garavito preyed on hundreds of boys across dozens of Colombian towns, though he focused largely on Pereira. There, he often disguised himself as a priest, farmer, elderly man, or street vendor, and lured in his victims with promises of money, candy, or employment.

Once he got them away from the crowds, Garavito earned their trust by asking them questions about their lives. Then, he attacked.

As Colombian police soon discovered, Garavito often subjected his victims to horrifying torture. He’d tie them up, rape them, bite them, and sometimes cut off their genitals or their toes.

By the time he was arrested in 1999, Luis Garavito had killed hundreds of victims. He confessed to killing some 140 boys, and even drew maps to lead police to their bodies, but Colombian authorities suspect that Garavito’s victim count is much higher. He may have killed as many as 400.

That makes Luis Garavito one of the worst serial killers — if he’s judged by the jaw-dropping number of his victims. But in the United States, that title may belong to someone else.

The Horrifying Crimes Of The Green River Killer

In the United States, the worst serial killer may be Gary Ridgway, who is known as the Green River Killer. Between 1982 to 1998, he murdered at least 40 women — but may have murdered more than 90.

Getty ImagesGary Ridgway was sentenced to life in prison in 2003, after narrowly avoiding the death penalty.

Born in 1949, Ridgway had a seemingly normal childhood marred by his chronic bedwetting. His mother reportedly washed his genitals after these humiliating incidents, which is why some psychologists believe that Ridgway developed a deep hatred of his mother (who escaped his killing spree).

After stabbing a boy at the age of 15 just to see how stabbing « worked » Ridgway became a murderous adult who targeted vulnerable women and girls. He started killing in 1982 by murdering 16-year-old Wendy Lee Coffield, a foster home runaway, and rapidly escalated.

Ridgway targeted runaways and sex workers, who he often picked up at bars or truck stops along Highway 99 outside Seattle. He would try to earn his victims’ trust by talking about his son. Then, Ridgway have sex with them, strangle them to death, and dump their bodies along Green River.

By the time he was arrested in 2001, Ridgway had lost count of his victims. He was eventually convicted of 49 murders, but confessed to 71, and may have killed even more. « I killed so many women, I have a hard time keeping them straight, » Ridgway admitted in 2003.

Gary Ridgway is certainly one of America’s worst serial killers and has long been considered the most prolific murderer in the country. But there’s another killer who might have gruesomely outdone him: Samuel Little.

Luis Sinco/Los Angeles Times via Getty ImagesSamuel Little appears unfazed after being convicted on three counts of first degree murder on Tuesday, Sept. 2, 2014, in Los Angeles Superior Court.

Little confessed to killing 90 women between 1970 and 2005 across more than a dozen states, and the FBI was able to verify that he’d been involved in the deaths of 60 of his alleged victims. Eerily, the authorities were able to confirm many of Little’s kills thanks to drawings he’d made of his victims.

When it comes to the worst serial killer in the United States, then, both Gary Ridgway and Samuel Little are fair candidates given their large (and somewhat vague) victim count. But based on notoriety alone, the worst killer in the U.S. might be Ted Bundy.

Ted Bundy, One Of America’s Worst Serial Killers

All of the killers in the gallery above killed in horrible, gruesome ways. But Ted Bundy stands apart for the bloodthirsty way he murdered his victims. In just four years between 1974 and 1978, Bundy raped and murdered some dozens women across seven states. He confessed to killing 30, but his true victim count could be much higher.

Bettmann/Contributor/Getty ImagesTed Bundy waves to television cameras during his trial for the assault and murder of several women in Florida in 1978.

Bundy, who was born in 1946 and had a turbulent childhood, attacked his first known victim in 1974. Then, he broke into the apartment of 18-year-old Karen Sparks and bludgeoned and raped her with a metal rod from her bed frame. Sparks survived with her life — barely — but Bundy’s future victims would not be so lucky.

He continued attacking young women in Washington and Oregon, often luring them in by pretending to struggle with a crutch or a stack of books near his infamous Volkswagen Beetle, before he left town to study at the University of Utah. There, Bundy continued to kill, often targeting teen girls.

From Idaho to Colorado to Florida, Ted Bundy continued his spree. He was finally arrested on Feb. 15, 1978, in Florida when a police officer pulled him over for erratic driving and discovered several women’s IDs in his possession. Soon afterwards, the gruesome details of Bundy’s crimes came to light, leading one investigator to note: « I would describe him being as close to being like the devil as anyone I ever met. »

But Bundy, Gary Ridgway, and Luis Garavito are just some of the world’s worst serial killers. Look through the gallery above to learn the stories of some of the other « real life » monsters who once stalked dark streets.

For more nightmare fuel, check out some of the creepiest quotes from serial killers or find out about the most terrifying female serial killers of all time.