This empirical study was the first to explore the criminal life course of people imprisoned in a Dutch facility for uncontrollably violent persons as a consequence of prison violence ( N = 383). Their characteristics were compared with those from studies of Dutch incarcerated people and those of persons residing in an in-prison psychiatric facility ( N = 1,913). Results showed that uncontrollably violent detained persons are an extreme group: their criminal life course is characterized by an early onset, an extensive and severe criminal career, and high scores on most violence-related historical risk factors. The severity and early onset of their criminal life course, their problematic behavior, and their problems in other life domains became even more apparent following our comparisons. This study underlines the relevance of detained persons’ pre-prison characteristics in addressing prison violence risk factors, and shows that early detection and monitoring is essential to prevent (more) damage.