Source: heroesvillainsandsidekicks.com

8. Dr. Alchemy

Everyone knows Two-Face. Everyone loves Two-Face. But where's the love for some of the other split-personality supervillains?

There are a bunch of them. And a lot of them are pretty cool. Especially Albert Desmond.

Desi started his criminal career under the name Mr. Element, with a freaky gas mask and a special pistol. After The Flash hauled him to jail, Albert discovered the legendary Philosopher's Stone (which, unlike the Sorcerer's Stone, is a thing), and went through a successful re-branding to become Dr. Alchemy. Also, he had a twin brother named Alvin, who turned out to not even be real, because Dr. Alchemy is a weird character with a needlessly complicated history.

Desmond's weird planning also ran afoul of The Batman when he started setting up bonus labs in Gotham City. This caused the GCPD to team up with the KCPD in a fantastic arc of Gotham Central.