10. Mockridge's Breakdown - Batman The Animated Series
A personal favourite of mine, If You're So Smart, Why Aren't You Rich? is the 40th episode of Batman: The Animated Series and marked the show's debut of the Riddler. Here, Edward Nygma is reimagined as a disgruntled software designer who received no royalties for creating the hit Riddle of the Minotaur video game. He's fired by the head of the company that's taken advantage of him, Daniel Mockridge, and returns two years later as the Riddler, determined to get his revenge.
The episode itself features loads of brilliant set-pieces, with Riddler kidnapping Mockridge and forcing Batman and Robin to navigate a real life Minotaur labyrinth to save him, but it also packs a genuinely unsettling conclusion.
In one of the rare instances of a villain evading justice in the series, the episode ends with Riddler getting away. We later learn that Mockridge sells his company and pockets a cool $10 million, but he's still clearly petrified at the thought of Riddler returning to finish the job.
As Bruce Wayne and Dick Grayson reflect on the affair, we're left with a chilling glimpse into how the ex CEO is coping. He's seen anxiously bunkering down into his bed with a shotgun, as Bruce asks one final riddle: "how much is a good night's sleep worth?"