It's really hard to say. Naruto in his strongest form, like when he has the power of all the tailed beasts, is extremely powerful. He has incredible strength, speed, and the ability to use a vast array of jutsu. However, Aang in the Avatar state has access to all four elements and can be a formidable opponent. If we consider the Avatar state's spiritual connection, it could give Aang an edge in a battle of wills.
Sesshomaru could also be a very powerful character in this crossover. He has his own powerful sword, Bakusaiga, and his inhuman strength and speed. He is very experienced in combat against demons. Compared to Naruto's friends like Sakura, Sesshomaru would likely be much more powerful in terms of raw strength and combat ability. But Sakura has her own medical ninjutsu and superhuman strength when she releases her inner power, which could also be useful in different situations.
The clash of different power systems is a major draw. When Naruto from his world of chakra crosses over to a world like One Piece with Devil Fruits and Haki, the comparison and interaction of these power systems create a lot of exciting plot possibilities. Readers are always curious to see how the power - scaling works and which character would be stronger in a fight when different universes collide.
One popular 'powerful naruto crossover fanfiction' is 'Naruto in the World of Bleach'. It combines the elements of Naruto's ninja skills with the Soul Reaper world of Bleach in an exciting way. The story often has Naruto showing off his unique jutsus in the face of Hollows and Soul Reapers.
Well, Erza is a very strong character in Fairy Tail. She has a vast array of armors and combat skills. However, in a crossover, Sasuke could be a real contender for the most powerful. His Sharingan gives him amazing abilities like predicting moves and copying techniques. And his Rinnegan in later arcs makes him even more formidable. But then again, characters like Gildarts from Fairy Tail are also extremely powerful with their unique magic. So it really depends on how the crossover is written and what abilities are emphasized.
It's likely that Naruto himself would be one of the most powerful. His ability to use chakra and his various jutsu like the Rasengan would give him an edge in combat. He also has the Nine - Tails' power which could be a game - changer.
Sasuke would also be very powerful. His Sharingan gives him enhanced perception and the ability to copy moves. In the SAO world, he could quickly analyze the fighting styles of opponents and come up with counter - strategies. His Chidori and other lightning - based jutsu could be very effective against the digital enemies in SAO.
I think Doomguy could also be a top contender. His experience in fighting demons, his arsenal of powerful weapons, and his unwavering determination would make him a strong character in the Naruto - Doom crossover. He might not have chakra, but his combat skills are top - notch. If he were to learn some basic ninja techniques, he could become even more powerful.
However, we can't forget about Steve. He has been living in the Minecraft world for a long time. He has in - depth knowledge of how to build the most powerful weapons and structures. He can use his pickaxe with great skill, which could be as effective as a ninjutsu in some cases. Also, his ability to survive in the Minecraft world's harshest conditions gives him an edge over the Naruto characters who are new to this environment.
It could be Naruto in his Sage of Six Paths mode. He has incredible power, with the ability to fly, use various powerful jutsus, and his chakra is off the charts. In a fight against the characters from Toriko, his speed and strength would be very difficult to match.