Across Avatar: The Last Airbender and its spinoff projects, there have been plenty of villains Big or small, cunning or idiotic, deadly or toothless, outright evil or possibly good, there is nothing all the villains of Avatar have in common other than the fact they need more screen time.
Prequel projects give an unparalleled ability to explore the rich history of a source material's characters without disturbing the status quo of their original stories. While comics like Katara and the Pirates Silver and the Kyoshi novels delve into the past of the world, they should not be so quick to manufacture new antagonists for the heroes to face off against. With that said, let's look at some villains in the Avatar world that deserve some attention.
June & Nyla
With almost none of her backstory depicted in the original series, the bounty hunter June was essentially the Boba Fett of Avatar. Morally apathetic and unbelievably cool, she and her shirshu Nyla were introduced in the Season 1 episode "Bato of the Water Tribe" and returned in the series finale to aid the heroes. Given that her backstory comes from the unofficial Lost Lore of Avatar, she still has plenty left to explore.
Trained by her father in the arts of combat and tracking, June became the best bounty hunter in the world. Her father gifted her Nyla at an early age and the two grew up together, so their shared backstory is ripe for prequel storytelling. Regardless of if a story went far enough back to show June's father teaching her the ropes or hit the ground running with the champion arm-wrestler first establishing her solo reputation, there is no doubt it would be a memorable fixture in the franchise.
Cram enough backstory into a tight enough place and you're bound to get fans demanding more. Such is the case with Yakone, the Republic City crime boss best known in The Legend of Korra as a unique and powerful bloodbender that fathered the main antagonist of the show's first season. Much of Yakone's past remained a mystery throughout the bulk of the show, and since the primary threat was Amon, there was little time to delve into Amon's father.
So, a prequel could explore Yakone first established power and what remained of his criminal empire after he left. Watching the rise of a gangland king could make for an interesting story all its own, and any prequel that shows Aang and his friend's adventures as adults in the fledgling Republic City would almost need to address Yakone by necessity. Intersperse it with Amon's journey from the North Pole honing himself into the revolutionary figure he would one day become, and there may be a villain-centric story with legs of its own in the works.
Not every villain is prone to delivering monologues potent with backstory and exposition, and, in fact, some don't speak at all. The silent assassin that creates a big boom came to be known as Combustion Man as he doggedly pursued them in the original series' third season. So little was revealed about him, though, that it goes without saying fans need to know more.
Again the Lost Lore comes in handy, providing the backstory that Combustion Man struggled with his unique abilities at an early age where the consequence of using them cost his limbs. Just how the mysterious subskill of combustion bending works would be fascinating on its own, but combining it with the heart-wrenching story of a boy forged into a merciless mercenary could form one of the best stories in the franchise.
Hama only ever appeared in one episode of Avatar, but given that it's one of the most memorable entries in the series, there is a whole lot more story potential waiting to be mined. At first appearing as a harmless innkeeper, Hama quickly turned out to be one of the most demented villains the Gaang ever faced as she revealed she was a Southern Water Tribe Waterbending who escaped imprisonment from the Fire Nation by inventing the art of bloodbending.
Given her advanced age and the ambiguity of her timeline, there are potentially entire decades where the sadistic Waterbender lived in enemy territory. A prequel could explore whether the Fire Nation ever sent hunters like Combustion Man or June after such a threat, or if she connected in any way to Yakone, who claimed to be from a line of the world's greatest Bloodbenders. With that potential, Hama could very well be at the center of the ultimate villain prequel story.
The Red Lotus
Receiving more screentime than any of the other villains on this list, it could be argued that the Red Lotus had plenty of space. The difficulty with that point of view is that they were each so monumentally interesting that without a prequel, there is no adequate way to satisfactorily cover their backstories. The anarchist group of master benders so powerful they could dismantle the world (and nearly succeeded) has a huge black spot in their history, and that's a problem.
While it's been revealed that Xai Bau founded the Red Lotus after growing discontent with the legendary White Lotus, little else is known about the group's history between then and the attempting kidnapping of a young Avatar Korra. Seeing the rest of the group interact with Unalaq, only revealed to be a member in the show after his death, and seeing their dynamics and personalities previous to becoming escaped convicts would be worth it. Show firsthand Zaheer rescuing P'Li from the warlord exploiting her as a child, and give virtually anything to Ghazan and Ming-Hua's backgrounds and fans will eat it up. Few of the members can even appear in future stories, so there's no way to go but the prequel route.