Lex Luthor could be a great villain. He could be after some technology in Spiderman's world that he wants to use to enhance his power in his own battles against Superman. At the same time, he might see Wonder Woman as a threat to his plans of world domination. He could use his intelligence to create complex traps and weapons. His corporate power would also allow him to manipulate situations in both the worlds of Spiderman and Wonder Woman.
Cheetah could be a great villain. She has a connection to Wonder Woman already, but in a crossover, she could be working with some of Batman's rogues like the Penguin. The Penguin could provide the resources while Cheetah does the dirty work in combat against Batman and Wonder Woman.
Athanatos could be a great villain. He's a powerful and immortal being who has been sealed away for centuries. But with the disruption of ancient magic (maybe caused by Lara's latest adventure), he is freed. He wants to conquer both the mortal and the Amazonian worlds. Lara's knowledge of archaeology and Wonder Woman's combat skills would be put to the test against his dark magic.
Spiderman's agility and ability to climb walls combined with Wonder Woman's super strength could make them an unstoppable team. For example, Spiderman could use his web - slinging to quickly get Wonder Woman to high vantage points, from where she can use her strength and lasso to take on enemies. Or in a fight, Spiderman can dodge attacks and then Wonder Woman can follow up with her powerful punches.
Circe could be a great villain. She has powerful magic and could create all sorts of illusions and obstacles for Wonder Woman and Hawkgirl. She might try to turn them against each other or use their powers for her own dark purposes.
The Green Goblin could also fit well. He could form an alliance with some of Wonder Woman's foes. His chaotic nature and love for destruction would contrast with the heroes' quest for peace. He could target both of them, trying to break their partnership and cause mayhem in the city.
A powerful alien warlord could be the main villain. This warlord might have his eyes on Earth because of its resources or strategic location. Supergirl and Wonder Woman would have to use their unique powers and teamwork to defeat him. He could have an army of minions and advanced technology that makes him a formidable foe. They would need to figure out his weaknesses and come up with a plan to stop his invasion.
Well, it depends on the situation. If the fight takes place in the Naruto universe where Naruto can draw on natural chakra more easily and has the home - field advantage, he could be very strong. He also has his Nine - Tails chakra which is extremely powerful. On the other hand, Wonder Woman has years of combat training and her divine weapons. In a battle of wits and strategy, Naruto's experience in fighting various opponents in his world might give him an advantage, but Wonder Woman's overall power set is also very formidable.
Brainiac could also work well. He is an android with an insatiable thirst for knowledge and a penchant for collecting and destroying planets. In a crossover, he could target Earth, specifically Gotham and Metropolis. His advanced technology would pose a major challenge to both Superman and Batman. Superman's super - powers would be put to the test against Brainiac's powerful defenses, and Batman would need to use his wits to find a weakness in Brainiac's systems, leading to an exciting and complex story.
Another possibility is that there is a villain who is stealing technology from Stark Industries (where Spiderman sometimes gets his tech) and ancient artifacts from Wonder Woman's homeland. They are both independently investigating and then cross paths and decide to work together to stop the thief.
Maybe there's a powerful ancient artifact that has been stolen and is being used for evil purposes. This artifact has the power to disrupt the balance between different realms. Spiderman discovers some strange happenings in the city related to the artifact's power, like buildings randomly changing shape. Wonder Woman is also on the hunt for the artifact as it was stolen from a place under her protection. When they meet, Spiderman is initially in awe of Wonder Woman's strength and beauty. They team up, with Spiderman using his acrobatic skills to navigate through dangerous traps set up by the villains protecting the artifact, and Wonder Woman using her lasso of truth to find out where the artifact is hidden.