Another plot twist could be that the attacker was actually under the control of a mind - controlling villain. When Bucky subdues the attacker, the villain realizes that Bucky is onto him. So, the villain then tries to frame Bucky for the attack on the girl, forcing Bucky to clear his name while still protecting the girl from the real threat that the villain poses.
In this fanfic, the girl could be on her way home from work when suddenly she was set upon by an assailant. Bucky, with his enhanced senses, detected the danger. He arrived just in time. His metal arm gripped the attacker's weapon - hand tightly. 'You picked the wrong person to mess with today,' Bucky growled. The girl stared at Bucky in awe as he saved her. Afterward, she thanked him profusely, and Bucky just gave her a small smile, his blue eyes showing a hint of kindness beneath his tough exterior.
One possible plot twist could be that Naruto's closest friend turns out to be secretly working for the enemy. Just when Naruto is about to make a final stand against the invaders, his friend betrays him, leaving him in a difficult situation. But Naruto, being Naruto, manages to find a way to turn the situation around and still save the village.
A possible plot twist could be that Bardock actually saves Broly, but in doing so, he unknowingly sets in motion a chain of events that leads to an even greater threat. For example, by saving Broly, he might disrupt the balance of power among the Saiyans in a way that angers some powerful factions, who then form an alliance with an external enemy.
A plot twist might be that the oc has to team up with his enemies in the chaos realm to save Olympus. Or perhaps, when he saves Olympus, he accidentally unleashes another greater danger because of his chaotic powers. Maybe the gods who he saves end up betraying him because they fear his power as the son of chaos.
Well, a plot twist might be that when Naruto arrives to save Hinata, he finds out that Hinata has already made a deal with the Kumo ninjas for the sake of Konoha. So Naruto has to figure out how to honor Hinata's decision while still protecting her. Also, it could be that the Kumo situation is just a cover - up for a much larger conspiracy involving other villages. And there's a chance that the person Naruto thought was Hinata in danger was actually a clone, and the real Hinata is in an even more dangerous situation elsewhere.
A plot twist could be that when Arya saves her mom, they find out that there was a prophecy involved all along. The prophecy states that Arya's actions will set off a chain of events that will either save or doom the Seven Kingdoms. Now they have to decide what to do with this newfound knowledge and whether to act on it or try to keep it a secret.
One possible plot twist could be that the real danger was not what it seemed at first. For example, while the Avengers thought they were being attacked by a supervillain, it was actually a test set up by a greater power. And Peter discovers this truth while trying to save them. Another twist could be that Peter has to sacrifice one of his powers temporarily to save the Avengers, which changes his approach to being a superhero.
Perhaps the twist is that Sirius saves Draco, but in doing so, he sacrifices his own freedom. And then Draco has to figure out a way to return the favor and free Sirius. Or it could be that the reason Sirius saves Draco is not what it seems at first. Instead of pure altruism, he has a hidden motive related to his own past or a prophecy that involves Draco.
Well, perhaps the moment Bucky is squashed, he has a vision or a premonition. This vision could be about a future danger to Steve or to the world. Then the fanfic could shift into them trying to prevent this future event from happening. Or it could be that when Bucky is under Steve's weight, they are suddenly teleported to a different dimension, and they have to find their way back while also dealing with the new and strange things in that dimension.
One plot twist could be that the villains find out about Peter's newfound relation to Bucky before Peter and Bucky themselves do. They could then try to use this information to manipulate Peter or turn him against Bucky. Another twist might be that there is some sort of time - travel or alternate reality involved, and in this new reality, Bucky is Peter's father, but it was never meant to be in the original timeline. This would make Peter question his entire existence and his place in the multiverse.