It's likely to be Goku. His ability to constantly increase his power level through training and reaching new forms like Super Saiyan God and Ultra Instinct gives him an edge. He could potentially overpower most of the Bleach characters.
Rukia is also popular. Her connection to Ichigo and her own unique powers and backstory can be explored in new and exciting ways in reincarnation fanfics. For example, she might be reincarnated in a different part of the Soul Society with a new role to play.
Rukia can also be quite popular. Her connection to Ichigo and her own experiences in the Bleach universe can be interestingly explored in relation to hollowfication in fanfics. For example, how she might react to Ichigo's further hollowfication or if she were to face the threat of hollowfication herself.
Ulquiorra Cifer is often a popular character. His cool and somewhat mysterious demeanor in the original series makes him a great subject for fanfiction. Writers like to explore his inner thoughts and emotions more deeply, especially his relationship with Orihime.
It's hard to say for sure. Ichigo in his final form in Bleach has extremely high power levels. He can cut through almost anything with his sword and has great speed and strength. However, in Fairy Tail, Acnologia is a very powerful dragon slayer. His dragon form gives him incredible power and he has a lot of combat experience. So it could be either of them depending on how the fight is set up.
It's a tough call, but it could be Luffy. His Devil Fruit powers combined with his indomitable will make him extremely formidable. If he were to somehow gain some Soul Reaper abilities on top of that, like the ability to use a Zanpakuto, he would be near - unbeatable. His Gear Fourth form already gives him enhanced strength and speed, and with Soul Reaper powers, he could be a force to be reckoned with.
It's really hard to say who would be the most powerful. Saitama from One Punch Man (if we were to include him in this wild crossover thought experiment) would probably be a top contender just because he can defeat any opponent with one punch. But in a more traditional Bleach - Marvel crossover, if the Living Tribunal from Marvel was involved, it would be extremely powerful. It has near - omnipotent powers and oversees the entire Marvel multiverse. However, in Bleach, Yhwach has extremely powerful abilities as well, like the ability to see the future and rewrite it. So it really depends on the context and how the crossover is set up.
Well, characters like Rukia from Bleach are quite popular in 'juubi naruto and bleach fanfiction'. She has a strong sense of justice and her ice - based zanpakuto abilities can create interesting scenarios when paired with Naruto's Juubi - influenced powers. And from Naruto, Kakashi is also well - liked. His vast knowledge and combat experience can be a great asset in the crossovers. He might be the one to figure out how to bridge the gap between the two different power systems.
There are several popular original characters. One might be a character named Kai, who is often depicted as a powerful Soul Reaper with a mysterious past. He has unique sword - fighting skills that set him apart from the regular Soul Reapers in the fanfiction.
Sasuke can also be a very popular character. His complex personality and powerful jutsu can create interesting storylines in the 'naruto godlike bleach fanfic' world. He might have some sort of power - up or new relationships with Bleach characters. Also, characters like Rukia are popular as well. Her cool and calm demeanor along with her strong Soul Reaper abilities can make for great interactions with Naruto characters.