Ladd Russo is a sadistic hitman formerly affiliated with the Russo family, a Chicago-based mafia organization active during the Prohibition era of the 1930s. He is the nephew of Placido Russo, the head of the family, and leads a group of enforcers known as the White Suits, who dress in white tuxedos to make the blood of their victims stand out more vividly. Little is known about Ladd's early life or how he became the family's principal killer, but his defining trait is an insatiable love for violence and chaos. He experiences genuine, maniacal joy when fighting or killing, especially when his victims believe themselves to be invincible or unaware of their impending death. He derives particular pleasure from killing those who think they will never die, and he is happiest when surrounded by dead bodies or the sounds of gunfire. This obsession shapes his motivations: he does not kill indiscriminately, but targets members of rival organizations or arrogant individuals who act as though they are untouchable. He has little interest in killing those who expect death or are resigned to it, a quirk that sometimes leads him to spare certain opponents.

Despite his cruelty, Ladd is deeply attached to his fiancée, Lua Klein. Their relationship is a darkly romantic one: Ladd expresses his love for Lua through a passionate promise to kill her someday, and Lua appears to accept this fate without fear. This twisted affection highlights the complexity of his character, as genuine tenderness coexists with homicidal intent. Ladd's loyalty to the Russo family is pragmatic rather than devoted; he works for his uncle but remains fickle and self-interested.

In the story, Ladd plays a central role in the Flying Pussyfoot train arc. He boards the transcontinental train ostensibly to hunt down Jacuzzi Splot, whose gang had attacked Russo speakeasies, but also plans to use the journey as a bloody wedding trip. His group's intended massacre is thrown into disarray when the Lemures gang hijacks the train, and later when the legendary assassin Claire Stanfield, acting as the Rail Tracer, begins slaughtering both factions. Ladd clashes with multiple characters, including Chane Laforet and Jacuzzi's gang, and eventually loses an arm to Claire before being incarcerated. Throughout this arc, his relentless pursuit of pleasure in destruction serves as a catalyst for much of the mayhem.

Ladd's notable abilities include exceptional skill in hand-to-hand combat, particularly boxing, as he once killed a Lemures member with a single punch. He is also highly proficient with firearms and employs a theatrical, showman-like style in battle, blending brutality with flair. His psychological instability, however, can lead to reckless decisions that sometimes put him at a disadvantage against more calculating opponents. His development across the series is not one of redemption but of the evolution of his madness, as he becomes an increasingly stark embodiment of humanity's darker instincts.

Key relationships define his role. With Lua, his love is inseparable from violence. He holds a grudging respect for Isaac Dian, whose obliviousness to danger Ladd finds amusing rather than arrogant. He is disgusted by people who manipulate others through words and tricks, preferring direct confrontation. His rivalry with Claire Stanfield ends in his defeat and mutilation, marking a turning point in his arc. Ultimately, Ladd Russo stands as a charismatic, unpredictable antagonist whose sadistic nature and twisted romanticism make him one of the most memorable figures in the series.