Well, a cool plot twist might be if the Infinity Stones in the Power Rangers' universe have a different origin or power than expected. For instance, instead of granting power over space, time, etc., they might grant the ability to control the elements in a way that the Rangers haven't seen before. Or perhaps a Ranger is revealed to be a double agent working for the other side all along, which throws the whole team into chaos.
In a Power Rangers Infinity War fanfiction, a great plot twist could be that the source of the Rangers' power, like their Zords or Morphers, gets corrupted. This forces them to find a new way to fight. Also, what if there's a character from another Power Rangers series who shows up and has a connection to the Infinity War events? This new character could bring in a whole new set of powers and knowledge that either helps or hinders the Rangers.
One interesting plot twist could be that the Power Rangers' powers are somehow transferred to the villains. This would completely change the dynamic of the fight. Another could be that the Rangers are sent to an alternate dimension where the rules of the Infinity War are different. Maybe they have to team up with their former enemies just to survive.
One interesting plot twist could be that Loki uses his illusions not just to deceive Thanos but also to create a false Infinity Gauntlet. This would mislead Thanos and his minions, buying time for the Avengers to regroup. Another could be that Loki discovers a hidden power within himself that allows him to temporarily freeze the Infinity Stones' power, halting Thanos' plan.
A really cool plot twist could be that the Dementors from Harry Potter start attacking the cities protected by the Power Rangers and Ninja Storm. This forces the heroes from the latter two to seek help from the wizards in Harry Potter. And then, when they do get some magical assistance, it has unexpected side - effects on their powers. For instance, the Ninja Storm powers might start to have a magical glow or the Power Rangers' suits could gain some new, magical abilities. It would be a great way to blend the different elements of the three universes in a very unexpected way.
The Red Ranger would likely be a top contender for the most powerful. They usually have strong leadership skills and often the most powerful attacks among the team. However, if we consider villains, Rita Repulsa could be very powerful in an Infinity War scenario. With her magic and cunning, she could cause a lot of trouble for the Rangers.
A possible plot twist could be that Loki was actually working with Thanos all along, but faked his death to deceive the Avengers. This would change the whole dynamic of the story and lead to a new set of conflicts. Another twist could be that Loki's survival was part of a grand plan by Odin (who might not be truly dead) to stop Thanos from getting all the Infinity Stones.
Another plot twist could be that the powers of the Dino Thunder Rangers and the ninja abilities in Naruto are somehow related in a way that no one expected. Maybe the origin of ninjutsu was actually influenced by the same energy source that gives the Rangers their powers. This discovery could change the way both groups view their own powers and could lead to new alliances or conflicts within the fanfiction.
A plot twist could be that the main villain in the fanfiction is actually a character from one universe who has been corrupted by the power of the other. For example, a Naruto character who becomes evil after getting a hold of some Ninja Steel power. Or vice versa, a Power Ranger who is influenced by the dark chakra in the Naruto world.
A plot could involve the Rangers losing their powers temporarily and having to rely on their wits and teamwork more than ever. They could discover new, unexpected abilities within themselves while facing a powerful ancient enemy. For example, they might learn to combine their civilian skills in a way that gives them an edge in battle. This would add depth to their characters and show that being a Ranger is not just about having superpowers.
A fanfiction plot could be about a new threat that is specifically targeting the Omnitrix and the Power Rangers' power source. Ben and the Rangers have to figure out how the enemy is doing this and stop them. Along the way, they discover a hidden connection between the two power systems that was unknown before. There could be some character development for both Ben and the Rangers as they struggle to protect what they hold dear.
One idea could be a story where a new ranger from a different planet joins the SPD team. They have unique powers that the others don't, and at first, there's some tension as the team has to adjust to their new teammate. But eventually, they all work together to defeat a powerful new villain.
An interesting plot for Power Rangers OC fanfiction could be an OC who starts off as a villain's minion but then has a change of heart. This OC might be forced to do the villain's bidding at first, but through interactions with the Power Rangers, they see the error of their ways. They could then use their knowledge of the villain's plans to help the Rangers. Maybe this OC has a special ability that is crucial in defeating a major villain in the end.