He could be a strategic addition. His magic could be used for things like stealth, teleportation, and protection spells for the team. For instance, he could teleport members in and out of dangerous situations quickly.
He could be a valuable asset. His immortality means he has a vast amount of experience. He could use his magic to heal the injured members of the League quickly. For instance, with a spell like 'Episkey', he could mend wounds in seconds.
Harry Potter's powers would add a new flavor to the Justice League. His magic could be used for various things like teleportation which could be useful for quick rescues or getting to far - off battle sites. His Patronus charm could also be used as a form of protection or distraction against enemies.
Spiderman would bring his acrobatic skills and spider - sense. His ability to move quickly and dodge attacks would be very useful in Justice League battles. He could scale the walls of buildings during an urban fight, providing a different perspective and advantage.
He could fit as a powerful ally. His mastery over death gives him abilities that could enhance the Avengers' capabilities.
In a fanfic, Captain America could fit into the Justice League by being the voice of the common man. The Justice League often deals with big, cosmic threats, but Captain America would remind them of the importance of protecting the ordinary people on the ground. His experience in World War II gives him a unique perspective on the cost of war and the value of peace, which could influence the Justice League's decisions when it comes to using force and resolving conflicts.
In such a fanfic, Harry Potter as the Master of Death would bring a whole new dynamic to the Justice League. His magical abilities are different from the superpowers of the League members. He might have to adjust to the more scientific and modern world of the Justice League while still relying on his old magical knowledge. And the League would have to learn to work with his rather unorthodox methods.
The fanfiction could show Harry using his skills as the Master of Death to resurrect certain key characters in the Avengers universe who have died. This would change the power dynamics and relationships within the team. He could also use his magic to teleport the Avengers to different locations quickly, which is something that could be very useful in their fight against powerful enemies. Also, his understanding of the Deathly Hallows could lead to some interesting plot twists where the Avengers have to help him protect these powerful artifacts from falling into the wrong hands.
Naruto could fit in as a powerful ally. His ability to use chakra and his combat skills would be valuable. He could use his shadow clones to gather information or distract enemies. Against foes related to the Juubi, his experience in fighting powerful demons in his own world would come in handy.
Naruto would fit in by being the energetic and determined member. His loud and boisterous personality would contrast with some of the more reserved members of the Justice League. His physical abilities, like his superhuman strength and speed gained from his ninja training, would make him a valuable addition in battles.
Naruto's strong sense of justice and his will to protect his friends and village are qualities that would make him a great addition to the Justice League. He could relate to Superman's desire to protect the world and Batman's commitment to justice. Also, his growth as a ninja could be paralleled with the growth of the Justice League as a team, learning from each other's experiences and skills.