5. Amitai Marmorstein
Appeared in: Batwoman
Batwoman adapted the Batman mythos in some unique ways and its most successful example of that was in its third season. With the weapons of Batman's greatest enemies ending up in the wrong hands, it bred a new generation of villains that Batwoman and her team had to contend with. We got a new Killer Croc, a new Poison Ivy (as well as the original one), and even a new Mad Hatter.
This version was named Liam Crandle, and he was obsessed with Alice; the show's former big bad who was now undergoing a redemption arc that involved helping the Scarlet Knight's team solve crimes. Upon finding the Mad Hatter's hat, he was imbued with the ability to control anyone around him and that made him virtually impossible to stop - that is, until Alice managed to subdue him with surprise.
Amitai Marmorstein played Liam and he did a great job bringing the original character to life. But here's the thing; even though Liam was a character created for Batwoman, he actually came off like the original Mad Hatter, which made him that much more chilling. From the accidental villainy in the beginning to how he unnervingly began to take control of his actions (and people's minds), this was a Mad Hatter not to be trifled with, and Marmorstein's performance sold it to perfection.