The TV show Criminal Minds, which aired for nearly two decades, delved into the depths of humanity by exploring the minds of criminals and the FBI agents who pursued them. Each episode followed a case-of-the-week format, with some mysteries spanning whole seasons. While the Behavioral Analysis Unit always prevailed, some of the criminals, known as unsubs, left a lasting impact on viewers.

Some unsubs stood out for their unique and chilling nature, like Nathan, a young man who believed he was destined to become a serial killer. Another memorable unsub was an angry child named Jeffrey who targeted other kids.

A husband-wife duo, the Roycewoods, abducted children and their motives remained a mystery. Therapist Stanley preyed on his patients' fears, while the Replicator, played by Mark Hamil, mimicked other serial killers' methods.

Dark characters like Dr. Howard, a therapist turned killer, and cannibal Adam Rain left a lasting impression. Notable unsubs also include Cat Adams, a hitwoman, and Henry Grace, who sought revenge on a BAU agent. The Reaper, based on the Zodiac Killer, and Mr. Scratch, a hypnotist with a grudge, were formidable foes. Each unsub brought a new level of terror to the show, leaving viewers on the edge of their seats.