Active in early twentieth-century Japan, Fukiage targeted girls and women in a pattern of sexual violence that extended well beyond his confirmed killings. The scale of his offenses — with estimates reaching into the hundreds of victims — made him one of the most extensively documented predatory criminals of his era. His case was notable both for its duration and for the difficulty authorities faced in establishing the full scope of the harm he caused.

His criminal record stretched back decades before his most serious offenses, and he had been released on parole just a year before the murders began — a detail that shaped public and institutional responses to what followed. Over a matter of weeks in 1963, he sexually assaulted dozens of boys in Quebec and killed four of them, using a simple ruse involving a camera to gain their trust. The case drew significant attention to questions of parole oversight and the handling of repeat offenders in mid-century Canada.

His effectiveness as a suspect lay partly in his methods and partly in the failures surrounding him — a highly mobile, rootless existence made forensic tracing difficult, and poor coordination between French law enforcement agencies compounded the problem for years. Operating across dozens of departments with no fixed pattern of victim or location, he accumulated suspected cases that took decades to prosecute, including one in which an innocent man served fifteen years before exoneration. The investigator who came closest to understanding him noted that Heaulme never fabricated — he disclosed, but strategically, folding dates and locations together to obscure which crime was which.

Napper's crimes in early 1990s London included the rape and murder of Rachel Nickell on Wimbledon Common in 1992 — a case that became one of Britain's most scrutinized criminal investigations, partly because an innocent man was wrongly prosecuted for the killing before Napper was eventually identified. His conviction for that crime came only in 2008, more than fifteen years after the fact, following DNA evidence that linked him to a series of attacks across South London.

Kalinić operated during the Bosnian War of the 1990s, a conflict marked by widespread atrocities and ethnic violence across the former Yugoslavia. His nickname "Zver" — meaning "The Beast" — reflects the reputation he carried among those who documented the era's perpetrators. His case stands as part of the broader reckoning with wartime violence that international and domestic tribunals have worked to address in the decades since.

Over four years, Cooke moved through Perth at night committing a string of violent attacks that left eight people dead and a city in sustained fear. What amplified the damage of his crimes beyond his own actions was the wrongful conviction of two other men — Darryl Beamish and John Button — whose cases were only resolved decades later through the admissions Cooke made after his arrest. He was hanged at Fremantle Prison in 1964, the last execution carried out in Western Australia.

What distinguishes Ogata's case is the documented transformation — from a preschool worker described as gentle into an active participant in a killing spree that claimed at least seven lives, including members of her own family. Psychologists and observers have long pointed to her relationship with Futoshi Matsunaga as the mechanism of that change, with severe abuse and psychological control forming the backdrop to her involvement. The legal proceedings themselves were contested, with courts at different levels dividing over whether her role and circumstances warranted death or life imprisonment.

Duncan's criminal history spanned decades, with offenses beginning before his first imprisonment and continuing through periods of supervised release — a pattern that ultimately culminated in the 2005 Groene family attack in northern Idaho, which drew national attention for its particular brutality toward children. His case became a focal point in debates about sex offender monitoring and parole oversight, as authorities later connected him to additional murders committed while he was on parole in the mid-1990s. He died in federal custody in 2021, having accumulated multiple death sentences and life terms across three jurisdictions.

His career as an operative spanned continents and targeted civilian infrastructure at scale — a truck bomb beneath the World Trade Center in 1993, an airliner downed mid-flight over the Philippines, and the ambitious Bojinka plot, which envisioned the simultaneous destruction of multiple transoceanic flights. What distinguished him was operational ingenuity rather than organizational rank: he functioned largely outside formal hierarchy, yet produced attacks whose ambitions and methods anticipated the catastrophic terrorism of the following decade. His maternal uncle, Khalid Sheikh Mohammed, would later be accused of masterminding the September 11 attacks — a lineage of planning that underscores how much of what followed traces back to this period.