It's easy to forget that the entire series of Avatar: The Last Airbender takes place over the course of a single year as Aang learns to master the four elements in pursuit of restoring balance to the world. While the 12-year-old is successful in his pursuit, he is aided by other young prodigies of bending who expand their own powers throughout the course of the series.
If the entire cast's powers could grow so much over the course of a year, it only makes sense that the sequel comics would see those powers expand even further.
Up for consideration first is Aang: the series' star whose progress and training was the focus of the original series itself.
After his climactic battle with Fire Lord Ozai, Aang was assuredly the most powerful bender in the world, but he still had a lot left to learn. Surprisingly, Aang continues to default to using the airbending he already mastered by the series' start and rarely expands on what he does with the other elements.
That isn't to say Aang isn't more powerful, however. Now with the Avatar State mastered, Aang has used the godly force to rip trenches around entire cities, and even used his sphere composed of the four elements to head a giant earth kaiju in order to battle a giant rampaging spirit named General Old Iron.
What is most notable is not necessarily what Aang learns to do, however, but what he learns not to do. In the most recent comic, when faced with yet another evil bender, Aang ultimately chose not to remove their bending as he did with Ozai in the series' finale. His arc has always been about restraint more than power, but that's not quite true with all the other characters.
Far more willing to explore her new abilities is Aang's earthbending master Toph. A young prodigy herself, the Blind Bandit established herself during the original series as possibly the most powerful earthbender in the world. The comics reinforce that status when she holds up a collapsed mine all by herself for hours before help arrives. Such feats of strength are not even Toph's greatest achievements, however, and to find those one must look at the bending art she invented and mastered herself: metalbending.
While Toph first discovered the new bending style during the original series, her proficiency in it was always limited. Most often her metalbending relied on direct contact with the metal she shaped, whereas the comics quickly expand on her budding ability to bend metal at a distance.
She forms the Metalbending Academy to proliferate the artform even as she masters it, and eventually is so adept herself that she dismantles an entire army of tanks with a stomp of her foot, popping every vehicle's screw out of place.
Most recently, Imbalance: Part 3 saw Toph discover the usefulness of metal whips that would eventually become the main weapon of Republic City's police force she founded.
The power amps don't all go to Aang's allies, however, and perhaps the character most enhanced by the comics is series antagonist, Azula. While many of the other characters saw their powers grow throughout the original series, Azula's powers seemed to decline as she sunk further into madness that degraded the control and precision she was so famous for.
By time the comic, The Search, takes place, her madness had not quite worn off, but she did show that she regained some of her precision when she released both small zaps of lightning and wide blasts with an area of effect that could encompass a swarm of insects.
But to find Azula at her most powerful, fans must look to Smoke and Shadow. There, Azula is not only fully in control of herself, but maintains a ruse as a spirit known as the Kemurikage. She fights adeptly even without her bending, but once her identity is revealed it's no holds barred. Not only does she show that her proficiency with lightningbending has grown so much that she no longer needs windup to release powerful blasts, but Azula even demonstrates a new ability she never had before. She fires a blast of lightning at Zuko that Zuko then redirects, and Azula's response is to redirect the lightning right back at him.
It's not just benders that get all the power amp love, either. The Kyoshi Warrior, Suki gains the ability to chi-block from her teammate Ty Lee, releasing stunning jabs in combat that paralyze her opponents' limbs and makes it impossible for them to bend.
Suki was always a deadly force even before gaining the ability, and once she masters it so thoroughly she teaches an entire army the same skill. It's quite possible she's now the greatest non-bending fighter the Avatar World has ever seen.