If you combined Edward Elric and Eren Yeager, they would probably be very powerful. Edward has his alchemy skills which can be used for various things like creating weapons or barriers, and Eren has the ability to transform into a Titan. Together, they could use alchemy within the Titan form, perhaps creating stronger structures or weapons directly on the Titan's body.
A combination of Roy Mustang from Fullmetal Alchemist and Mikasa Ackerman from Attack on Titan could be quite powerful. Roy has his flame alchemy which is very destructive, and Mikasa is an extremely skilled fighter. In a battle, Roy could provide long - range support with his flames while Mikasa gets up close and personal with enemies. The combination of her combat skills and his alchemy would make them a formidable duo against any threat, whether it's Titans or the enemies from the Fullmetal Alchemist world.
Well, consider combining Alphonse Elric and Armin Arlert. Alphonse is a skilled alchemist, and Armin is known for his intelligence. Together, they could come up with some very clever strategies. Alphonse could use alchemy to create distractions or defenses, while Armin plans out the overall battle strategy. Their combined abilities would make them a force to be reckoned with. For example, they could use alchemy to create false landscapes to mislead enemies, while Armin figures out the best way to attack or escape depending on the situation.
Another powerful combination could be Scarlet Witch and Roy Mustang. Scarlet Witch's reality - warping powers and Roy Mustang's ability to control fire through alchemy. Together, they could create massive and unique attacks. The Scarlet Witch could manipulate the fabric of reality to enhance Roy's fire - based alchemy, making it even more destructive and unpredictable.
If we consider strategy and intelligence along with power, Levi from Attack on Titan could be a top contender. His incredible combat skills and quick thinking could make him a force to be reckoned with even among the superpowered heroes. But then there are heroes like Eraserhead who can nullify quirks, which could be a huge advantage against some of the more dangerous Attack on Titan characters.
Sasuke could also be a very powerful contender. His Sharingan and Rinnegan give him a lot of combat advantages. If he had Titan abilities, he could use his ocular powers to control and enhance the Titan form. He might be able to see the weak points of his enemies even more clearly in a Titan form and use his lightning - based jutsu more effectively, combined with the brute strength of the Titan.
I think Naruto and Alphonse Elric would make a really unique pairing. Naruto's ability to see the good in people and his constant pursuit of friendship could be a great influence on Alphonse, who has been through so much. On the other hand, Alphonse's calm and reflective nature could help Naruto think more deeply about his actions. Another interesting pair would be Sakura and Izumi Curtis. Sakura could learn a great deal from Izumi's tough - love approach to training and her strong alchemical skills. And Izumi could perhaps be inspired by Sakura's medical knowledge. And finally, Shikamaru and Scar would be an odd but interesting pair. Shikamaru's intelligence and Scar's complex view of the world could lead to some really thought - provoking discussions.
Well, in some fanfictions, you might see Edward Elric from Fullmetal Alchemist teaming up with Eren Yeager from Attack on Titan. They could combine their unique abilities. Edward's knowledge of alchemy and Eren's Titan - shifting power could be used to take on common enemies. For example, they might face a new threat that is a combination of the Homunculi from Fullmetal Alchemist and some new type of super - Titan in the Attack on Titan world. And the different character dynamics, like Edward's hot - headedness and Eren's determination, would make for an exciting story.
It's hard to say for sure, but Thor could be a very powerful character. His hammer gives him the ability to fly and strike with great force. Against the Titans, he could use his lightning powers to fry them. Also, his god - like strength and durability would make him a tough opponent for the Titans.
Saitama is clearly the most powerful. In the Attack on Titan world, the Titans are a huge threat. But for Saitama, they are just like any other weak opponent. He doesn't even break a sweat dealing with the most powerful threats in his own universe, so the Titans would be no match for him. His power is not only physical but also his unshakable will and his simplicity in approaching any fight. He doesn't get distracted or intimidated, which makes him an unstoppable force in any situation, including in a merged OPM and Attack on Titan universe.
Thor would be a strong contender. His god - like strength and the power of Mjolnir, or Stormbreaker, could be very effective against the Titans. He could fly in and smash the Titans with his hammer, and his lightning powers could also do significant damage.
It's hard to say. Thor has his godly powers and his hammer Mjolnir which gives him great strength. But in the 'Attack on Titan' world, Eren's Titan form is also extremely powerful. However, if we consider all - around power, Iron Man with his advanced technology and ability to constantly upgrade his suit might be the most powerful. He could analyze the Titans' weaknesses and come up with strategies to take them down.
It's hard to say for sure, but many would argue that Naruto could be extremely powerful. His ability to use chakra, perform various ninjutsu, and access the power of the Nine - Tails gives him a huge edge. However, characters like Thor with his godly powers and the Hulk with his incredible strength also can't be underestimated.