The Hundred Year War that plagued Avatar: The Last Airbender tore apart the Four Nations as the Fire Nation asserted their dominance over the rest of the globe, and without the Avatar to stop them, it seemed there was no other option. As Aang slept in his iceberg, waiting for the day he could reemerge and restore balance to the world, the Water Tribe only fell further into chaos, and one casualty of the carnage was the waterbender Hama.
As fans would learn in the show's third season, Hama was far from innocent herself. She developed the unique ability to bloodbend to escape prison and inflict her vengeance on the Fire Nation until Team Avatar stopped her. But what if all her evil could have accomplished some good? Could Hama have used her powers to assassinate Fire Lord Ozai?
Hama would certainly have enough reason to want revenge against Ozai. As a citizen of the Southern Water Tribe, she fought relentlessly against Fire Nation raiding parties that steadily diminished the number of waterbenders from her home. When she stood as the last waterbender remaining, they took her prisoner and then cruelly imprisoned her under harsh conditions to keep her from waterbending her way to freedom. When she discovered that the full moon imbued her with the strength necessary to bend the blood within organisms, inventing the art of bloodbending, she escaped and began to enact her revenge.
Unfortunately, Hama's revenge never seemed to exceed the ambitions of haunting a small Fire Nation village, establishing herself as a sort of boogeyman who kidnapped villagers every full moon to imprison them. Rather than turning her newfound powers on the military who raided her homeland or the royal autocrats who began the war in the first place, Hama seemed content to torture innocent villagers sadistically. That comes as a particular shame because Hama is one of the few individuals who could have stopped the Fire Lord years before Aang's awakening.
Though Ozai is frequently touted as one of the strongest firebenders in the world of Avatar, there is extremely little direct evidence to support that. His lightning is not considerably better than Azula's, and his showings during Sozin's Comet are inferior to both Iroh and Jeong Jeong. Aside from statements from dubiously canon sources like Avatar Extras and a brief insight into his training regimen during the comics, there is nothing substantial to say Ozai could beat Hama in a fight. Even granting that he was the most powerful firebender in the world, Hama's bloodbending grasp completely neutralized Aang with almost no difficulty.
Aang was a master airbender, and he already had waterbending and earthbending under his belt when Hama neutralized him. It was only specifically through mastering bloodbending that Katara could stop her. To that end, neither Ozai nor his military force could stand a chance against Hama during a full moon. Even apart from bloodbending, Hama's skills with waterbending were considerable, pulling droplets from thin air and slicing rocks apart. With the aid of her bloodbending it's hard to imagine that Ozai would stand a chance.
Though the date of Hama's escape from imprisonment is inexact, it's possible she could have ended the Hundred Year War before Ozai ever even came to power. Although Azulon was a prodigy much like his granddaughter Azula, even less is known about his firebending ability. The older man seemed quite feeble in the time leading up to his death. With that in mind, Hama could well have ended the Hundred Year War decades previously.
The world of Avatar would have been remarkably different if she took those actions. But, as ever, there is always a lesson buried in the mythology of Avatar, and when considering Hama's talents, that lesson is one about how much good is wasted when those with potential dedicate it toward petty revenge.