A lot of pressure is placed on Avatar Aang's shoulders and that's pretty cruel considering he's just a kid. The once 12-year-old boy (he's been 12 for a hundred years, though) is tasked with bringing balance back to his world or saving it. While his feats and accolades are commendable, they simply pale in comparison to what other cartoon or anime characters can do and have done.
We could debate all day that Avatar is not an anime, but it doesn't matter since that term is quite flexibly used. Hence, Aang is not exempted from the usual Shonen anime character power ranking-- his powers are even similar to some of them. For that matter, here are ten of those anime characters which ought to put fear in Aang's heart (Avatar form or not). For the sake of inclusivity, we'll only be including two Dragonball franchise characters, otherwise, this whole list will only be about them.
10 YAMI YUGI - YU-GI-OH!
As much as we'd like this to be a joke, it seems Yami Yugi from Yi-Gi-Oh! has a few aces up his sleeve against Aang. Sure, Aang can simply firebend and burn all his cards, but when those cards are the five pieces of Exodia the Forbidden One, Aang simply won't have a chance. Yugi will automatically win such a fight if ever that happens regardless of the rules.
Even with the Exodia cards, Yugi will still be able to summon some pretty terrifying monsters. He's also in possession of one of the three God cards, specifically Slifer the Sky Dragon, which is probably as powerful as Aang himself if not more so.
9 RYUK - DEATH NOTE
Being a Shinigami (Death God) from the anime Death Note has its perks. Apart from being functionally immortal and having the ability to kill everyone by writing their names on a notebook, you are also invisible to mortals. That means Ryuk is invisible to Aang, or anyone alive. You can't fight what you can't see and Aang will have to go into a deep trance just to be able to see and interact with spirits.
Meanwhile, Ryuk can simply write Aang's name in his Death Note and the fight will be over in a flash. It's too unfair and even with all the elements, Aang is still no match for someone like Ryuk.
8 ALUCARD - HELLSING
Here's another immortal being that will surely give Aang a hard time. Alucard, which is Dracula spelled backward comes from the anime Hellsing. He's a vampire and is even older than Aang. Like Ryuk, Alucard has several tricks that can render Aang's attacks and bending prowess useless.
For one, Alucard can turn into shadow, making himself immune to any physical attacks. He probably doesn't even need to do that. Alucard comes ready with superhuman strength, speed, and reflexes being a vampire. Even if Aang manages to endure any of Alucard's attacks, the king of vampires will simply keep growing stronger until he is powerful enough to destroy the world.
7 ISAAC NETERO - HUNTER X HUNTER
Both Chairman Isaac Netero from Hunter X Hunter and Aang have plenty in common. Netero's powers also need proper form and meditation before he can achieve godly strength. When he does, Aang will need more than four elements just to be able to endure Netero's attacks. Netero is essentially one of the top heavy hitters in Hunter X Hunter.
Like Aang, he's also more than a century old, but that doesn't diminish his capability one bit. If anything, his old age also seems to have given him even more strength. Netero's experience in life and combat makes even the adult Aang look like a whelp by comparison. Thankfully, Netero seems more like a person Aang will seek out for advice rather than a fight.
6 TRUTH - FULLMETAL ALCHEMIST
There are plenty of times where Aang's elemental bending skills become too cheaty. He uses all four elements like utensils without much repercussions. Such hubris will probably earn the ire of Truth from Fullmetal Alchemist. You see, Truth likes to punish mortals for "playing God" too much.
For that matter, Truth isn't even a person. It's more like a personification of the rules of physics or even metaphysics. He's the closest thing to a "God" in the Fullmetal Alchemist anime. When pitted against Aang, it's basically him versus the rules of the universe. We assure you, that will not end in the Avatar's favor.
5 ICHIGO KUROSAKI - BLEACH
Like Ryuk, Ichigo Kurosaki of Bleach is a Shinigami. However, he plays by a different rule and Aang probably won't have as much trouble seeing him compared to Ryuk. Even so, Ichigo is a bigger badass than Aang. He has a sword and was created for a more mature audience, meaning he has no qualms on slaying his enemies.
Moreover, Ichigo has proven to be capable of defeating godly beings who can bend even reality. What's even more amazing about Ichigo is that he was once a regular human being whereas Aang was already a gifted resurrection of previous Avatars.
4 NARUTO UZUMAKI - NARUTO
When it comes to dreaming big, Aang's got nothing on Uzumaki Naruto from Naruto/Naruto Shippuden. What we have here is the quintessential Shonen anime character whose goal is to be the very best. He has gradually inched his way to it. In terms of fighting capabilities, however, Naruto makes Aang look boring.
He can summon countless clones of himself, summon giant monsters, weaponize air (Rasengan), transform into someone/something else (transformation jutsu), and enter his omnipotent Sage Mode (basically his version of Super Saiyan). Once Naruto goes Sage Mode, no amount or length of Avatar Mode will save Aang.
3 SAITAMA - ONE PUNCH MAN
No matter how patient or peaceful Aang is, a fight with Saitama from One Punch Man would be enough to make him lose his composure. That's because any single attack Aang does will not connect or will not do anything. Saitama has parodically trained himself to the peak of Shonen fighting capacity.
Additionally, the bald unfair dude has fought faster and stronger opponents than the Avatar. Really, years of Avatar training would be worthless in the face of a comically unfair and self-aware hero who ends all fights with just one punch. Sorry Aang, there's only room in animated shows for one bald protagonist-- and he's meant to be funny.
2 SON GOKU - DRAGON BALL
This one's already a given. Goku from the Dragonball franchise is infinitely more powerful than Avatar Aang-- even as a kid with a monkey tail. We're talking about a Shonen guy (who's thankfully more serious than Saitama) who can obliterate planets as if they're just collateral damage. He has super strength, speed, reflexes, flight, and can channel energy into a death wave/ball.
More than that, Goku has more forms or tiers of power than Aang, namely Super Saiyan levels and he can even turn into a giant berserk ape. Even some of Goku's less powerful friends (or enemies) can squish Aang like a mere bug. Don't even get us started on Ultra Instinct, no need for that overkill form-- Aang's just a kid, have mercy.
1 ZENO/FUTURE ZENO - DRAGONBALL
Goku, as powerful as he is, is not the be-all, end-all being in the Dragonball franchise. In fact, many of his enemies are even more powerful than him. However, all of them are mere ants at the mercy of Zeno. He's one of the two entities who stands above and governs the multiverse in the Dragonball franchise. The other one is Future Zeno, who's also himself.
There's no limit to what Zeno can do. He can make everyone and everything vanish if he wills it, even someone as powerful as Goku. As a testament to his irrational powers, Zeno has already destroyed six of the original 18 universes out of anger. In that regard, Aang is about as significant as a molecule of a speck of dust to Zeno.