Perhaps the Green Goblin could be the villain. He's a classic Spiderman foe and could pose a real threat to both Spiderman and the Shadow.
It could be Kingpin. He has the resources and the power to cause trouble for both heroes. He could try to use their meeting to his advantage, like creating a divide between them and then taking over the city while they're distracted.
Venom could also be a great villain in this fanfiction. His dark and powerful nature would make him a formidable opponent for both Spiderman and the Shadow. He could target them separately at first and then try to take them both on when they team up.
It could be someone like Ra's al Ghul. He is a powerful and complex villain that both Batman and The Shadow would have a hard time dealing with. His global influence and long - life plans would pose a great threat to their efforts to protect Gotham and the world.
The Green Goblin could be a likely villain. He has a long history with Spiderman and his maniacal nature would put him at odds with both Spiderman and Deadpool. His glider and pumpkin bombs would be a real threat to them.
The Green Goblin would be really interesting. Imagine him getting his hands on a wand and trying to use magic in his own chaotic way. His maniacal laughter would echo through Hogwarts as he zooms around on his glider, causing mayhem.
Well, in this fanfiction, Spiderman might learn some new skills from the Shadow. The Shadow could have some unique fighting techniques or ways of moving around the city that Spiderman has never seen before. So, Spiderman could incorporate those into his own fighting style. Also, their personalities could clash at first. Spiderman is more of a talkative and quippy hero, while the Shadow is often more brooding and mysterious. But eventually, they could find common ground and work together really well.
In such a fanfiction, Spiderman and Shadow might initially be at odds. Spiderman, with his sense of justice and responsibility, could view Shadow as a threat due to his more brooding and sometimes violent nature. However, they might find common ground in fighting a greater evil. For example, a powerful villain that neither could defeat alone. They could combine their unique abilities, Spiderman's web - slinging and superhuman strength with Shadow's speed and chaos powers to take down the bad guy.
Maybe there's a new character, a mad scientist who has been observing both the Sonic and Bendy universes. He creates a device that can merge the two worlds in a chaotic way, causing disasters in both. He believes that by doing this, he can become the ruler of the combined universe. Bendy and Sonic must stop him before the two worlds are completely destroyed.
Dr. Eggman could be a great main villain. He might have a new plan that involves both the power of Sonic Underground's music and the Chaos Emeralds that Shadow guards. He could try to create a device that amplifies negative emotions through music and uses the Chaos Emeralds' power to spread chaos everywhere.
It's hard to say who would be stronger. Superman has incredible super strength, flight, and heat vision. But Spider - Man is extremely agile and has his spider - sense. In a direct physical fight, Superman might seem more powerful on the surface. However, Spider - Man's quick thinking and ability to use his environment could give him an edge in certain situations.
Kingpin would be a great antagonist. He already has a history with Daredevil and his criminal empire could easily draw in Spiderman as well. He could use his wealth and influence to create all sorts of problems for the two heroes, like funding new super - villains or using his political connections to turn the public against them.
It's not so straightforward though. Daredevil is a highly skilled martial artist and his enhanced senses could potentially allow him to anticipate Spiderman's moves. If the fight took place in a very enclosed and dark space, Daredevil might be able to use the environment to his advantage and land some good blows on Spiderman.