According to IMDb, two separate episodes of "Law & Order: Criminal Intent" stand at the top. Both the Season 6 episode "Endgame" and the Season 7 episode "Frame" currently have a rating of 9.2 stars out of 10. However, at the time of writing, "Endgame" has roughly 70 more votes, giving it a slight edge over its competition. It's worth noting that "Endgame" is not a typical episode of "Criminal Intent," which often saw the detectives temporarily become entangled in the lives of criminals and victims before solving the case and moving on with their work. Instead, this episode made the stakes alarmingly personal for Vincent D'Onofrio's Detective Goren.
"Endgame" sees Goren visit a serial killer on death row who has requested to meet him. The murderer, a man named Mark Ford Brady (played by Roy Schneider, no less), informs Goren that there is hidden evidence proving that he actually claimed more victims than was thought. As Goren and Eames search for the evidence, Goren discovers a terrible secret about his family. In one of the most shocking twists of the whole series, Goren learns that his now-ailing mother had an affair with Brady and that the serial killer is actually his true biological father.
It was a revelation that sent fans reeling and had major implications for the series going forward. As such, it's easy to see why this particular episode is viewed by many fans as the best episode of the "Law & Order: Criminal Intent" series.
