His role at the top of Japan's most powerful criminal organization came through violence rather than succession — stepping into leadership after the assassination of Masahisa Takenaka during one of the yakuza's most turbulent internal conflicts. The Yama–Ichi War, a bloody factional struggle within and around the Yamaguchi-gumi, defined the years of his tenure, and the instability of that period meant his authority was always contested in ways that formal leadership rarely is.

His significance lies less in violence than in architecture — the construction of a trafficking network that reshaped the synthetic drug trade across an entire region. After a US prison sentence that might have ended a lesser operation, he returned to build Sam Gor into a cartel reportedly responsible for a substantial share of the methamphetamine flooding Southeast Asia. Investigators drew comparisons to El Chapo, though Tse operated with a deliberate low profile, relying on intelligence and discretion rather than force to sustain what became one of the largest drug enterprises in modern history.

His position of institutional authority — as both nurse and nursing home manager — gave him sustained, unsupervised access to the most vulnerable patients over an extended period. The scale of his confirmed killings, at least 22, made him one of Norway's most prolific convicted killers, and his case raised lasting questions about oversight within care facilities.

A professional background in bacteriological chemistry lent an unsettling dimension to a case that spanned more than a decade of largely undetected violence against women and girls in Mexico City. Cortés Miranda was only apprehended after his final killing, at which point skeletal remains discovered in his apartment implicated him in further deaths — the full scope of which will never be formally established. His death before trial closed the investigation prematurely, leaving open questions about additional missing persons cases linked to his name.

One of the most prolific hired killers of the late frontier era, he operated for years beneath a veneer of religious respectability — regular church attendance, no drinking, no smoking — while accepting contracts on human lives. The contradiction between his public piety and his profession as a gunman for hire made him a singular figure in the record of Old West violence.

His career in Lyon between 1942 and 1944 made him one of the most documented perpetrators of Gestapo brutality in occupied France, responsible for the deportation of Jewish children and the systematic torture of resistance members. What distinguishes his case historically is not only what he did during the war but what followed: U.S. intelligence sheltered him afterward, West German intelligence later recruited him, and he spent decades advising South American regimes on methods of repression before finally facing trial in 1987.

Travis came to investigators' attention in an unusual way: he sent a taunting letter to a reporter, but used an online map service to generate a printout that contained traceable metadata, leading to his arrest. Evidence recovered at his home suggested the actual number of victims extended well beyond the two murders cited in the federal complaint. He died by suicide in custody before facing trial.

Over a three-year span in Siberia, Kozlenya carried out a methodical series of killings targeting private car drivers, shooting them after hailing rides under the pretense of ordinary fares. His crimes followed a consistent pattern — a concealed weapon, a pre-arranged destination near a rented garage, and the subsequent dismantling of vehicles for parts — suggesting a premeditated, if ultimately self-defeating, criminal enterprise. The involvement of a coerced underage accomplice added a further dimension to the case, though she was ultimately acquitted.