One possible motive could be power. Maybe he thinks that by kidnapping the Pink Ranger, he can gain some sort of advantage over the other Rangers or access some hidden power. Another motive might be revenge. If he has some sort of grudge against the Pink Ranger or the whole Ranger team, this could be his way of getting back at them.
Perhaps Tommy is jealous of the Pink Ranger. Maybe she has something that he desires, like a special ability or a connection to someone or something. He might think that by kidnapping her, he can either take that thing for himself or simply stop her from having it. It could also be that in this fanfiction, Tommy has a different backstory that makes him see the Pink Ranger as a threat to his goals, whatever they may be.
She could use her martial arts skills. The Pink Ranger is usually trained in combat. So, when Tommy least expects it, she could deliver a powerful kick or punch and make a run for it.
In 'Adam and Tommy MPreg Power Ranger Fanfiction', a recurring theme could be the protection of the unborn. Adam and Tommy would have to face various threats, not just from villains but also from the potential reactions of the outside world. This could lead to themes of secrecy, sacrifice, and the lengths they would go to protect their family - to - be. Additionally, themes of love and commitment between the two main characters are bound to be prominent, as they navigate this unexpected journey together.
It could be that Naruto has lost his sanity temporarily. The stress of being a hero, the constant battles, and the losses he has endured might have taken a toll on his mental state. In this state of instability, he may see Sakura as a symbol of something he wants to preserve or protect, but his way of doing so is through kidnapping. Or there could be a new villain in the story who has the ability to make Naruto act out of character, and this villain's plan involves Naruto kidnapping Sakura.
Well, it could be out of jealousy. Maybe Dean feels like he's losing Ginny to someone else and in a moment of madness, decides to kidnap her. But this is all just speculation within the wild world of fanfiction.
It could also be for power. Perhaps Stiles has some knowledge or ability that Theo wants to use for his own gain. In the show, Stiles was quite smart and resourceful, so Theo might kidnap him to get access to that intelligence or those skills. In some fanfictions, Theo might be trying to use Stiles as a bargaining chip to get something from the other characters like Scott or Derek.
Tommy in the 'tommy good story' could be anyone. He might be a child with a vivid imagination and a heart full of goodness. Or he could be an adult who has had some remarkable experiences. Maybe he's a local hero in the context of the story, someone who is known for his positive actions.
I'm not sure of specific fanfictions on this topic. But you can try searching on popular fanfiction websites like Archive of Our Own (AO3). They have a large collection of Power Rangers fanfictions, and you might be able to find some related to Adam and Tommy in the MPreg genre.
One possible motive could be revenge. Maybe Sam Gh did something to Manny Ruiz in the past that made Manny want to get back at him.
Well, in this kind of fanfiction, Doc Oc could kidnap Spiderman to force him to reveal his identity. Doc Oc might think that knowing who Spiderman really is would give him an upper hand in their ongoing battles. It could also be that Doc Oc wants to study Spiderman's powers. He's a scientist after all, and Spiderman's abilities are quite unique. He might believe that by kidnapping and examining Spiderman, he can find a way to replicate or counter those powers.
The plot might involve Tommy being a rival of Felicity in some sort of competition. His actions during the competition, like cheating or using underhanded tactics, could hurt Felicity's chances of winning. This would create a lot of tension between them and could lead to a series of events where Felicity tries to expose Tommy's wrongdoings.