Final answer:
Edwin H. Sutherland is considered by some as the single most important criminologist of the 20th century. He is known for his differential association theory, focusing on the social learning of criminal behavior.
Step-by-step explanation:
The individual considered by some to be the single most important criminologist of the 20th century, according to a referenced work in the question, is Edwin H. Sutherland. Sutherland is known for his theory of differential association, which suggests that criminal behavior is learned in interaction with other people through a process of communication. This theory shifts the focus from the individual's characteristics to the social context within which behavior is learned. His work has been influential in the field of criminology, affecting both theoretical developments and practical applications in the criminal justice system. Moreover, Sutherland's ideas continue to inspire and challenge researchers, policymakers, and practitioners within the realm of criminology and sociology.