Well, the Black Ranger might also be a good match. He is a strong leader among the Power Rangers. Batman, being a natural leader himself, could respect the Black Ranger's leadership style. Together, they could lead a combined force of Gotham's vigilantes and the Power Rangers against a powerful enemy, coordinating their teams' efforts and using their combined resources to the fullest.
Sailor Mercury and Batman could be likely allies. Sailor Mercury is intelligent and tech - savvy, much like Batman. She could help him with any technological problems he might face in his fight against crime, while he could offer her his combat and detective expertise. For instance, if there was a villain using advanced technology to cause chaos in both their worlds, they could pool their knowledge to stop the bad guy.
Alfred is always a likely ally. His knowledge and experience can provide valuable support to Batman. Also, Oracle (Barbara Gordon) could be an important ally, using her hacking skills to disrupt any technology Superman might use or to gather information.
I think Klaus and Loki could be likely allies. They both have a sense of mischief and are often underestimated. They might team up to outwit their more 'righteous' counterparts. Klaus has his vampire powers and Loki has his Asgardian magic and trickery.
Inuyasha and Thor could potentially be allies. They both have a sense of honor and are very powerful warriors. Thor with his hammer and Inuyasha with his sword could fight side by side against powerful enemies. Also, Captain America and Inuyasha might get along. Captain America would respect Inuyasha's fighting skills and determination, and Inuyasha would see Captain America as a worthy leader.
Naruto and the Red Ranger could be a great pairing. Naruto is full of energy and determination, and the Red Ranger is often the leader. They would both lead their respective teams in a combined battle. Another good one could be Sasuke and the Blue Ranger. Sasuke has his cool and calculating nature, similar to the more strategic Blue Ranger.
Ruby and the Red Ranger would likely form an alliance. Ruby is a natural leader in RWBY, and the Red Ranger often takes the lead in the Power Rangers team. Their shared sense of responsibility and courage would bring them together. They could inspire each other in combat and strategy.
Goku could be a likely ally. Despite their initial conflicts, Goku has a way of seeing the good in people. He might approach Broly and convince him that they can work together to win the Tournament of Power for their universe. Their combined strength would be a formidable force.
I think Sam from Danny Phantom would get along well with Black Widow. They both have a no - nonsense attitude and are strong - willed. Sam could teach Black Widow about environmental protection, and Black Widow could train Sam in more hand - to - hand combat skills. Also, Tucker might be an ally to Iron Man. Tucker's love for technology and his skills in that area would make him a great partner for Tony Stark. They could collaborate on creating new gadgets that combine Danny's ghostly technology with Stark's high - tech creations.
Jean Grey would also be a likely ally. Her telepathic and telekinetic powers are extremely powerful. She could communicate with Superman on a mental level and use her powers to support him in battle. Plus, she has experience dealing with powerful threats, much like Superman, so they could work well together.
I think Sans and Iron Man could be great allies. Sans is intelligent in his own way in Glitchtale, with his knowledge of timelines and shortcuts. Iron Man is a tech genius. They could combine their knowledge to create strategies against common enemies. Iron Man might be intrigued by Sans' magic - like abilities and try to find a scientific explanation for them. Sans, on the other hand, would be impressed by Iron Man's high - tech gadgets.