One idea could be a crossover where Ben Tennyson and Spider - Man team up to stop a common enemy like Doctor Octopus who has somehow gotten his hands on some of the Omnitrix's alien DNA. They could combine their powers and skills to outwit the villain.
Well, 'ultimate spider man lemon fanfic' might be a fan - created story about Ultimate Spider - Man with some unique twists. It could be significant as it allows fans to explore different scenarios and relationships within the Spider - Man universe that may not be part of the official canon. It gives a platform for creative interpretations and can attract a niche group of fans who are interested in this particular type of fan - made content.
One idea could be creating an OC with a unique power set related to sound, like being able to manipulate sound waves for various effects such as creating sonic blasts or using echolocation. Another could be an OC who is a foreign exchange student from a technologically advanced country and brings in new gadgets to help Spider - Man. Maybe an OC who has a power to heal others but at a cost to their own health.
Maybe a villain who can transform into different animals. He could use this power to stalk Spider - Man in the city, changing forms to blend in and then attack when least expected. This would keep Spider - Man on his toes as he tries to figure out the pattern of the villain's attacks and how to counter this shape - shifting ability.
One idea could be Spider - Man teaming up with a new, original superhero created just for the fanfic. They could face a villain who has the power to manipulate time, causing chaos in New York. Another could be exploring what would happen if Spider - Man lost his powers temporarily and had to rely on his wits and the help of his friends to stop a crime wave.
Another possibility is that some sort of cosmic event makes them both super - charged, Naruto becoming godlike and Spider - Man reaching an ultimate form. They are then chosen to stop an interdimensional threat that could destroy both their worlds. They would have to learn to trust each other quickly and use their combined powers to save the day.
A great way to combine them is through a shared technology. Maybe some of the tech from the Omnitrix gets mixed up with Oscorp technology. This creates new villains or new powers for our heroes. They then have to figure out how to deal with these new situations. It could also lead to some interesting character development as they learn from each other. For example, Ben could teach Spider - Man about the different alien cultures he has encountered through his travels, and Spider - Man could show Ben how to better handle the public and keep his identity a secret in a big city.