What made Merrett so remarkable as a criminal case was the combination of audacity and impunity — he shot his mother, beat his wife and mother-in-law to death decades later, and spent the intervening years as a fraudster and black marketeer, all while largely evading the consequences that would have stopped most criminals far earlier. His first trial ended in the distinctly Scottish verdict of "not proven," a legal ambiguity that effectively freed him despite strong suspicion, and the full scope of his crimes only became clear long after the damage was done. The gap between what he did and what he was made to answer for remains the defining feature of his story.

As second-in-command of the AUC, Mancuso operated at the apex of a paramilitary structure responsible for some of Colombia's most devastating civilian massacres during the country's long internal conflict. The organization he helped lead carried out violence under the banner of anti-guerrilla operations, but the toll fell heavily on rural communities with no combatant role. His eventual demobilization and cooperation with investigators offered partial accounting — though his extradition to the United States on drug trafficking charges underscored how deeply the AUC's operations were entangled with the cocaine trade that fueled the broader conflict.

His appearances in Islamic State execution videos in 2014 and 2015 made him one of the most recognizable figures in the group's propaganda campaign, his masked presence and English accent carrying deliberate psychological weight aimed at Western audiences. The videos, which documented the killings of journalists and aid workers, were understood as sophisticated media productions as much as acts of violence. He was killed in a targeted drone strike in Raqqa in November 2015.

His control over the Branch Davidians combined theological authority with physical coercion, allowing him to maintain dominance over a closed community whose members had few means of exit or recourse. Allegations of polygamy and child sexual abuse preceded the federal attention that culminated in a 51-day armed standoff, ultimately ending in fire and the deaths of more than seventy people inside the compound. The siege at Waco became one of the most scrutinized confrontations between a religious sect and federal law enforcement in American history, raising questions about both the conduct of the government response and the nature of the community Koresh had built.

His influence operated through institutions as much as through direct action — a boarding school he co-founded became a pipeline for a network linked to some of Southeast Asia's deadliest attacks, including the 2002 Bali bombings that killed over 200 people. Intelligence agencies and the United Nations identified him as the spiritual head of Jemaah Islamiyah, a designation he contested, though his later public pledge of allegiance to ISIL's leadership underscored the ideological commitments that defined his decades of activity.