Mr. Krabs might be the most powerful in a different sense. If he were a Sith, his greed for power and wealth could drive him to be extremely ruthless. He'd stop at nothing to get what he wants, and his business acumen could be used to manipulate the Star Wars economy and gain more power than others. He could use his money to hire mercenaries and build his own army, making him a powerful force in the fanfiction.
It's hard to say for sure, but Anakin Skywalker could be a strong contender. His raw power in the Force, especially before his fall to the Dark Side, was immense. If he were to face off against a Voltron Paladin, his ability to use the Force to predict attacks and his lightsaber skills would be a formidable combination. However, the Black Paladin of Voltron also has leadership and combat skills that could give Anakin a run for his money.
It's hard to say for sure, but Superman has a lot of raw power. His physical strength, speed, and durability are off the charts. However, in the Star Wars universe, the Force can be extremely powerful too. If someone like Yoda or Palpatine fully utilized the Force against Superman, it could be a very close match. But Superman's ability to fly and his heat vision give him an edge in a straight - up fight most of the time.
It's really hard to say. Superman has incredible strength, speed, and a whole bunch of other powers. But then you have characters like Darth Sidious who are extremely powerful in the Force. If they were to face off, it would depend on the situation. Maybe in a physical fight, Superman would have the upper hand, but Sidious could use the Force to manipulate and deceive. So it could go either way.
Sasuke might also be a strong contender. His Sharingan gives him an edge in combat and perception. In a Star Wars setting, he could use his Sharingan to predict his opponents' moves in lightsaber duels or even sense the presence of the Force in a unique way. And his thirst for power could drive him to master both ninjutsu and the Force quickly.
Goku would be a strong contender. His ability to reach new levels of power through Super Saiyan forms and his combat skills could make him very powerful in the Star Wars universe. He could potentially use the Force in addition to his ki.
Ultimately, it depends on how the crossover is written. If it's a story that focuses on technological superiority, then Iron Man or some of the more tech - savvy Avengers could be the most powerful. They could create new weapons or devices that give them an advantage. But if the story is more about spiritual and magical powers, then the Jedi and Sith would likely be the most powerful. For example, if the story is set in a way that the Avengers have to adapt to the rules of the Star Wars universe, then the characters who can quickly master the Force would be the most powerful.
Darth Vader also has a strong claim. His mastery of the Force, along with his combat skills and his leadership in the Galactic Empire, would make him a formidable opponent. If he were to somehow get his hands on some Marvel - style technology or powers, he could become even more powerful. For example, if he were to combine his lightsaber skills with Wolverine's healing factor, he would be nearly unbeatable.
I think Qrow could be really powerful in this crossover. He has his own unique abilities in RWBY, and if he were to also master the Force, especially the more combat - oriented aspects like telekinesis to throw his weapon with more force or use the Force to enhance his reflexes, he'd be a force to be reckoned with. He also has a lot of experience in combat which would help him adapt to the new powers.
It could be Naruto himself. His ability to tap into the Nine - Tails' chakra gives him an incredible power boost. In the merged universe, he might be able to use the Force as well, which would make him an unstoppable force. With his speed, strength, and now potentially the power of the Force, he could easily defeat most opponents.
It's hard to say for sure, but Master Chief could be a strong contender. His combat training and advanced armor give him an edge. However, Darth Sidious is extremely powerful with his dark side abilities. He could potentially manipulate Master Chief if he got the chance. But then again, the Forerunners from Halo have such advanced technology that they might be able to counter the Force -powers. So it really depends on how the story is written.